staging: drm/omap: use current time for page-flip event

Because we don't have vblank hooked up via drm_irq (which is a bit
awkward due to separation between omapdss (which knows the irq #)
and omapdrm, for now use gettimeofday to have a semi-sane timestamp
in the page-flip event.  Otherwise apps like weston drm compositor,
which use the timestamp in it's animations, get highly confused.

Signed-off-by: Rob Clark <rob@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>