drm/amdgpu: update type for num_syncobj_handles in drm_amdgpu_userq_signal

drm/amdgpu: update type for num_syncobj_handles in drm_amdgpu_userq_signal

update the type for num_syncobj_handles from __u64 to _u16 with
required padding.

This breaks the UAPI for big-endian platforms but this is deliberate
and harmless since userqueues is still a beta feature. It is enabled
via module parameter and need the right fw support to work.

Signed-off-by: Sunil Khatri <sunil.khatri@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>