drm/omap: remove divider constraint from hsdiv

The driver only uses even dividers for hsdiv when pclk >= 100MHz, as odd
dividers can create uneven duty cycle. However, while this holds true
for some dividers like DISPC's LCK and PCK dividers, it is not actually
true for hsdiv.

hsdiv always produces even duty cycle, so the constraint can be removed.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>