OMAP: Remove flash unlocking from the mapping driver

Since commit 'e619a75ff6201b56' every MTD partition can
be marked with MTD_POWERUP_LOCK flag  which means the partition
will be unlocked upon kernel bootup. By default all
Intel's chips with instant individual block locking feature
have MTD_POWERUP_FLAG set. So we do not need to unlock
the flash in the mapping driver anymore.

Signed-off-by: Dmitry Krivoschekov <dmitry.krivoschekov@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>