powerpc/msi: Free the bitmap if it was slab allocated

powerpc/msi: Free the bitmap if it was slab allocated

During the MSI bitmap test on boot kmemleak spews the following trace:

unreferenced object 0xc00000016e86c900 (size 64):
    comm "swapper/0", pid 1, jiffies 4294893173 (age 518.024s)
    hex dump (first 32 bytes):
	00 00 01 ff 7f ff 7f 37 00 00 00 00 00 00 00 00
	.......7........
	ff ff ff ff ff ff ff ff 01 ff ff ff ff
	ff ff ff
	................
	backtrace:
	[<c00000000003eebc>] .zalloc_maybe_bootmem+0x3c/0x380
	[<c000000000042d6c>] .msi_bitmap_alloc+0x3c/0xb0
	[<c000000000a9aff8>] .msi_bitmap_selftest+0x30/0x2b4
	[<c0000000000090f4>] .do_one_initcall+0xd4/0x270
	[<c000000000a8e250>] .kernel_init_freeable+0x1a0/0x280
	[<c000000000009b5c>] .kernel_init+0x1c/0x120
	[<c000000000007fbc>] .ret_from_kernel_thread+0x58/0x9c

Add a flag to msi_bitmap for tracking allocations from slab and memblock
so we can properly free/handle memory in msi_bitmap_free().

Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
[mpe: Reword changelog & use bitmap_from_slab in the if]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>