include/uapi/drm/amdgpu_drm.h: use __u32 and __u64 from <linux/types.h>

Kernel headers exported to userspace are supposed to use these.

Fixes compilation errors in userspace:

error: unknown type name ‘uint64_t’
error: unknown type name ‘uint32_t’
Signed-off-by: Mikko Rapeli <mikko.rapeli@iki.fi>