[ARM] 4957/1: Drop special macro SCOOP_REG in favour if ioread16/iowrite16.

Make scoop driver use generic purpose io routines: ioread16
and iowrite16 instead of direct writing to memory.

Signed-off-by: Dmitry Baryshkov <dbaryshkov@gmail.com>
Acked-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>