sh: mach-rsk: Update for parse_mtd_partitions() fallout.

The RSK+ setup code was doing some pretty dubious things with
parse_mtd_partitions() in order to populate the physmap-flash map
platform data. The physmap-flash driver contains all of the functionality
that we require already, so simply drop the special casing and pad out
the platform data accordingly.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>