ARM: 7024/1: simpad: Cleanup CS3 accessors.

- prepend CS3 accessors by simpad_ to indicate they
  are specific to simpad devices.
- use spinlock to protect shadow register.
- implement 8 read-only pins.
- use readl/writel macros so barriers are used where
  necessary.
- register CS3 as GPIO controller with 24 pins
  (16 output only and 8 input only).
- fix PCMCIA driver to access the read-only pins
  rather than the shadow register for status bits.

Signed-off-by: Jochen Friedrich <jochen@scram.de>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>