msm: kgsl: Avoid copying aux_command_generic struct twice

In kgsl_ioctl_gpu_aux_command, kgsl_gpu_aux_command_generic struct
is copied to kernel before calling into kgsl_drawobj_add_timeline
and it is copied again inside kgsl_drawobj_add_timeline as part of
get_aux_command. Avoid this by directly passing user pointer and
size need by kgsl_drawobj_add_timeline to get the timeline command
struct.

Change-Id: Ic6e4e8a79484c85070f1feda516bbb0c0ace83eb
Signed-off-by: Deepak Kumar <dkumar@codeaurora.org>