Revert "modesetting: Indirect the glamor API through LoaderSymbol"

This reverts commit dd63f717.

Caused a crash at least on some systems.

Closes: xorg/xserver#934
3 jobs for revert-modesetting-indirect in 6 minutes and 12 seconds (queued for 28 seconds)
Status Job ID Name Coverage
  Docker Image
passed #952734
debian-testing

00:00:31

 
  Build And Test
passed #952735
autotools-build-and-test

00:05:40

passed #952736
meson-build-and-test

00:03:04