drm: tiny: Add support for Mayqueen Pixpaper e-ink panel

Introduce a DRM driver for the Mayqueen Pixpaper e-ink display panel,
which is controlled via SPI. The driver supports a 122x250 resolution
display with XRGB8888 format.

Also, add a MAINTAINERS entry for the Pixpaper driver.

Signed-off-by: LiangCheng Wang <zaq14760@gmail.com>
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://lore.kernel.org/r/20250902-drm-v5-3-d77c678c4ae3@gmail.com