backlight: pcf50633-backlight: Remove unused driver

The pcf50633 was used as part of the OpenMoko devices but
the support for its main chip was recently removed in:
commit 61b7f892 ("ARM: s3c: remove all s3c24xx support")

See https://lore.kernel.org/all/Z8z236h4B5A6Ki3D@gallifrey/



Remove it.

Signed-off-by: "Dr. David Alan Gilbert" <linux@treblig.org>
Link: https://lore.kernel.org/r/20250311014959.743322-8-linux@treblig.org


Signed-off-by: Lee Jones <lee@kernel.org>