mesa: FramebufferParameteri parameter checking

Missing break; causes parameter checking to
never pass GL_FRAMEBUFFER_FLIP_Y_MESA parameters.

Fixes: 318c2651 ("mesa: GL_MESA_framebuffer_flip_y extension [v4]")
Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
(cherry picked from commit 60d0c0d0)