feature-removal-schedule.txt: remove the NCR53C9x entry

Now that the driver is removed we should also remove the entry in
Documentation/feature-removal-schedule.txt

Signed-off-by: Adrian Bunk <bunk@kernel.org>
Acked-by: Christoph Hellwig <hch@lst.de>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>