ARM: 5682/1: Add cpu.c and dev.c and modify some files of w90p910 platform

Add the cpu.c and dev.c and modify w90p910 platform
to apply to use the common API(provided by cpu.c and dev.c)
at the same time, I renamed all w90x900 to nuc900 in every
c file of w90x900 platform and touchscreen's driver name.

Signed-off-by: Wan ZongShun <mcuos.com@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>