Revert "egl: drop empty eglfallbacks.c" and "egl: move fallback calls to eglapi.c"

Revert "egl: drop empty eglfallbacks.c" and "egl: move fallback calls to eglapi.c"

This reverts commits cc4b68a80193e2a132cb62309292984a9428f2bb and
b27fb3eacab906ec06cd61b7d01e3425c3b3cbfc.

These caused a bunch of EGLSync tests to crash when they were previously
failing.

I have a hunch the tests are doing something wrong, like using
extensions without checking for they support, but until the issue is
investigated I'm just reverting these commits.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>