backlight: remove ProGear driver

This driver was for the ProGear webpad device which was produced in
2000/2001 and is not available on a market.  I no longer have this
hardware so can not even check how Linux works on it.

Signed-off-by: Marcin Juszkiewicz <marcin@juszkiewicz.com.pl>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>