kms-winsys: don't wait for a flip when page flipping fails
kms-winsys: don't wait for a flip when page flipping fails

If we get EACCES from drmPageFlip we're not going to get
a flip event and shouldn't wait for one.

This commit changes the EACCES path to silently ignore the
failed flip request and just clean up the fb.

https://bugzilla.gnome.org/show_bug.cgi?id=756926

djdeath/cogl,djdeath/cogl,djdeath/cogl