ARM: PL061: Checking register r/w accesses to reserved area

pl061.c emulates two GPIO devices, ARM PL061 and TI Stellaris, which
share the same read/write functions (pl061_read and pl061_write).
However PL061 and Stellaris have different GPIO register definitions
and pl061_read()/pl061_write() doesn't check it. This patch enforces
checking on offset, preventing R/W into the reserved memory area.

Signed-off-by: Wei Huang <wei@redhat.com>
Message-id: 1455814580-17699-1-git-send-email-wei@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
