[MTD] [MAPS] Drop now unused sharpsl-flash map

Now as all PXA Zaurii are converted to use the physmap map,
drop the sharpsl-flash map completely.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>