mtd: remove redwood map driver

Removing the redwood mtd mapping driver, because all REDWOOD_[456]
configuration options were removed from the kernel, because they weren't
referenced anywhere.

Signed-off-by: Christian Dietrich <qy03fugy@stud.informatik.uni-erlangen.de>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>