randr: Remove funky indirection around the xf86 screen private key

All of the null checks here are redundant, you can't get to those paths
unless RANDR's already been initialized. Delete them, and remove the
pointer too.

Signed-off-by: Adam Jackson <ajax@redhat.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
2 jobs for less-randr-private-indirection in 1 minute and 25 seconds
Status Name Job ID Coverage
  Docker Image
passed debian-testing #78775


  Build And Test
passed build-and-test #78776