usb: dwc2: fix flags for DMA descriptor allocation in dwc2_hsotg_ep_enable

usb: dwc2: fix flags for DMA descriptor allocation in dwc2_hsotg_ep_enable

dwc2_hsotg_ep_enable can be called from interrupt context, so all
allocations should be done with GFP_ATOMIC flags. This fixes following
issue on ARM architecture:

[<c010d830>] (unwind_backtrace) from [<c010a51c>] (show_stack+0x10/0x14)
[<c010a51c>] (show_stack) from [<c032930c>] (dump_stack+0x74/0x94)
[<c032930c>] (dump_stack) from [<c011cd30>] (__warn+0xd4/0x100)
[<c011cd30>] (__warn) from [<c011cd7c>] (warn_slowpath_null+0x20/0x28)
[<c011cd7c>] (warn_slowpath_null) from [<c0187e04>] (smp_call_function_many+0xcc/0x2a4)
[<c0187e04>] (smp_call_function_many) from [<c0188014>] (on_each_cpu_mask+0x38/0xa8)
[<c0188014>] (on_each_cpu_mask) from [<c01ddfe0>] (start_isolate_page_range+0x134/0x1b8)
[<c01ddfe0>] (start_isolate_page_range) from [<c01a3c14>] (alloc_contig_range+0xac/0x2f8)
[<c01a3c14>] (alloc_contig_range) from [<c01de3e4>] (cma_alloc+0xe0/0x1a8)
[<c01de3e4>] (cma_alloc) from [<c0110acc>] (__alloc_from_contiguous+0x38/0xe0)
[<c0110acc>] (__alloc_from_contiguous) from [<c0110ba4>] (cma_allocator_alloc+0x30/0x38)
[<c0110ba4>] (cma_allocator_alloc) from [<c0111034>] (__dma_alloc+0x1c0/0x2c8)
[<c0111034>] (__dma_alloc) from [<c01111b4>] (arm_dma_alloc+0x3c/0x48)
[<c01111b4>] (arm_dma_alloc) from [<c04ad800>] (dwc2_hsotg_ep_enable+0xec/0x46c)
[<c04ad800>] (dwc2_hsotg_ep_enable) from [<c04da610>] (usb_ep_enable+0x2c/0x3c)
[<c04da610>] (usb_ep_enable) from [<c04dc0c0>] (ecm_set_alt+0xa8/0x154)
[<c04dc0c0>] (ecm_set_alt) from [<c04d678c>] (composite_setup+0xd74/0x1540)
[<c04d678c>] (composite_setup) from [<c04ae048>] (dwc2_hsotg_complete_setup+0xb8/0x370)
[<c04ae048>] (dwc2_hsotg_complete_setup) from [<c04d987c>] (usb_gadget_giveback_request+0xc/0x10)
[<c04d987c>] (usb_gadget_giveback_request) from [<c04acafc>] (dwc2_hsotg_complete_request+0x78/0x128)
[<c04acafc>] (dwc2_hsotg_complete_request) from [<c04aed28>] (dwc2_hsotg_epint+0x69c/0x81c)
[<c04aed28>] (dwc2_hsotg_epint) from [<c04af6c4>] (dwc2_hsotg_irq+0xfc/0x748)
[<c04af6c4>] (dwc2_hsotg_irq) from [<c0163264>] (__handle_irq_event_percpu+0x58/0x140)
[<c0163264>] (__handle_irq_event_percpu) from [<c0163368>] (handle_irq_event_percpu+0x1c/0x58)
[<c0163368>] (handle_irq_event_percpu) from [<c01633dc>] (handle_irq_event+0x38/0x5c)
[<c01633dc>] (handle_irq_event) from [<c01666e4>] (handle_fasteoi_irq+0xc4/0x19c)
[<c01666e4>] (handle_fasteoi_irq) from [<c0162a2c>] (generic_handle_irq+0x18/0x28)
[<c0162a2c>] (generic_handle_irq) from [<c0162b40>] (__handle_domain_irq+0x6c/0xe4)
[<c0162b40>] (__handle_domain_irq) from [<c0101470>] (gic_handle_irq+0x50/0x9c)
[<c0101470>] (gic_handle_irq) from [<c010b00c>] (__irq_svc+0x6c/0xa8)

Fixes: 5f54c54b0ba83 ("usb: dwc2: gadget: Add DDMA chain pointers to
	dwc2_hsotg_ep structure")
Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>