drm/imx/ipuv3: Compute dumb-buffer sizes with drm_mode_size_dumb()

drm/imx/ipuv3: Compute dumb-buffer sizes with drm_mode_size_dumb()

Call drm_mode_size_dumb() to compute dumb-buffer scanline pitch and
buffer size. The hardware requires the framebuffer width to be a
multiple of 8. The scanline pitch has to be large enough to support
this. Therefore compute the byte size of 8 pixels in the given color
mode and align the pitch accordingly.

v5:
- fix typo in commit description

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Philipp Zabel <p.zabel@pengutronix.de>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Sascha Hauer <s.hauer@pengutronix.de>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Fabio Estevam <festevam@gmail.com>
Link: https://lore.kernel.org/r/20250821081918.79786-11-tzimmermann@suse.de