drm/v3d: fix copy_from_user() error codes

The copy_to/from_user() function returns the number of bytes remaining
to be copied, but we want to return -EFAULT on error.

Fixes: e4165ae8

 ("drm/v3d: add multiple syncobjs support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Melissa Wen <mwen@igalia.com>
Signed-off-by: Melissa Wen <melissa.srw@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211011123303.GA14314@kili