Fix error code to correct pointer type

Fix error code to correct pointer type

To return an errno code inside a pointer,
the error code must first be converted to
the correct pointer type.

drivers/media/v4l2-core/v4l2-of.c:
In function 'v4l2_of_alloc_parse_endpoint':
drivers/media/v4l2-core/v4l2-of.c:227:10: warning:
return makes pointer from integer without
a cast [-Wint-conversion]
return -ENOMEM;

drivers/media/v4l2-core/v4l2-of.c:254:9: warning:
return makes pointer from integer without
a cast [-Wint-conversion]
return rval;

Bug 200187768

Change-Id: I757fe1f51559a0d0cda7463fd5541fac20e3a92e
Signed-off-by: Joe Korty <joe.korty@ccur.com>
Signed-off-by: Gaurav Singh <gaursingh@nvidia.com>
Reviewed-on: http://git-master/r/1163930
GVS: Gerrit_Virtual_Submit
Reviewed-by: Bibek Basu <bbasu@nvidia.com>