sparc64: mmu_context: Add missing include files

Fix the following build errors.

In file included from arch/sparc/include/asm/mmu_context.h:4:0,
                 from include/linux/mmu_context.h:4,
		 from drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.h:29,
		 from drivers/gpu/drm/amd/amdgpu/amdgpu_amdkfd.c:23:
arch/sparc/include/asm/mmu_context_64.h:22:37: error:
	unknown type name 'per_cpu_secondary_mm'

arch/sparc/include/asm/mmu_context_64.h: In function 'switch_mm':
arch/sparc/include/asm/mmu_context_64.h:79:2: error:
	implicit declaration of function 'smp_processor_id'

Fixes: 70539bd7 ("drm/amd: Update MEC HQD loading code for KFD")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>