drm/tilcdc: verify fb pitch

LCDC hardware does not support fb pitch that is different (i.e. larger)
than the screen size. The driver currently does no checks for this, and
the results of too big pitch are are flickering and lower fps.

This issue easily happens when using libdrm's modetest tool with non-32
bpp modes. As modetest always allocated 4 bytes per pixel, it implies a
bigger pitch for 16 or 24 bpp modes.

This patch adds a check to reject pitches the hardware cannot support.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Darren Etheridge <detheridge@ti.com>
Signed-off-by: Jyri Sarha <jsarha@ti.com>