compositor: Replace shift and conv opcodes by convh in BGRA SOURCE operator

Potentially speeds up processing a bit.
17 jobs for compositor-ayuv-source in 60 minutes and 27 seconds (queued for 2 minutes and 41 seconds)
Status Job ID Name Coverage
  Preparation
passed #316669
gst indent

00:00:33

passed #316668
manifest

00:00:49

 
  Build
passed #316670
build fedora x86_64

00:09:02

passed #316671
build nodebug fedora x86_64

00:09:02

 
  Test
passed #316672
check fedora

00:05:01

passed #316673
integration testsuites fedora

00:09:34

 
  Full Builds
passed #316675
build cerbero android universal

00:15:34

passed #316676
build cerbero cross win32

00:11:36

passed #316677
build cerbero cross win64

00:06:48

passed #316674
build cerbero fedora x86_64

00:07:21

 
  Full Tests
passed #316681
valgrind bad

00:08:29

passed #316678
valgrind base

00:08:45

passed #316682
valgrind ges

00:06:40

passed #316679
valgrind good

00:09:58

passed #316680
valgrind ugly

00:02:24

 
  Apps
passed #316683
android universal examples

00:11:44

 
  Deploy
passed #316684
documentation

00:03:20