ARM: OMAP2: select ARM_AMBA if OMAP3_EMU is defined

ARM: OMAP2: select ARM_AMBA if OMAP3_EMU is defined

This patch selects ARM_AMBA if OMAP3_EMU is defined because
OC_ETM depends on ARM_AMBA, so fix the link failure[1].

[1],
arch/arm/kernel/built-in.o: In function `etm_remove':
/home/tom/git/omap/linux-2.6-omap/arch/arm/kernel/etm.c:609: undefined
reference to `amba_release_regions'
arch/arm/kernel/built-in.o: In function `etb_remove':
/home/tom/git/omap/linux-2.6-omap/arch/arm/kernel/etm.c:409: undefined
reference to `amba_release_regions'
arch/arm/kernel/built-in.o: In function `etm_init':
/home/tom/git/omap/linux-2.6-omap/arch/arm/kernel/etm.c:640: undefined
reference to `amba_driver_register'
/home/tom/git/omap/linux-2.6-omap/arch/arm/kernel/etm.c:646: undefined
reference to `amba_driver_register'
/home/tom/git/omap/linux-2.6-omap/arch/arm/kernel/etm.c:648: undefined
reference to `amba_driver_unregister'
arch/arm/kernel/built-in.o: In function `etm_probe':
/home/tom/git/omap/linux-2.6-omap/arch/arm/kernel/etm.c:545: undefined
reference to `amba_request_regions'
/home/tom/git/omap/linux-2.6-omap/arch/arm/kernel/etm.c:595: undefined
reference to `amba_release_regions'
arch/arm/kernel/built-in.o: In function `etb_probe':
/home/tom/git/omap/linux-2.6-omap/arch/arm/kernel/etm.c:347: undefined
reference to `amba_request_regions'
/home/tom/git/omap/linux-2.6-omap/arch/arm/kernel/etm.c:392: undefined
reference to `amba_release_regions'
arch/arm/mach-omap2/built-in.o: In function `emu_init':
/home/tom/git/omap/linux-2.6-omap/arch/arm/mach-omap2/emu.c:62:
undefined reference to `amba_device_register'
/home/tom/git/omap/linux-2.6-omap/arch/arm/mach-omap2/emu.c:63:
undefined reference to `amba_device_register'
make: *** [.tmp_vmlinux1] Error 1
making modules

Signed-off-by: Ming Lei <tom.leiming@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Tony Lindgren <tony@atomide.com>