drm: sti: remove event lock while disabling vblank
drm: sti: remove event lock while disabling vblank

Stop use event_lock in vblank disable function.
This was creating a dead lock.

Signed-off-by: Benjamin Gaignard <6ee0a5bd5732730b243a6755a8505d5db9232205@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs