drm/omap: remove align_pitch()

The previous commit removed aligning the pitch to SGX's pitch
requirement from align_pitch(). What's left is effectively a function
that returns width * bytespp.

To clean up the driver, we can remove the function and have the
calculation inline in the two places which call align_pitch().

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