gpio: Make gpio-msm-v1 into a platform driver

Doing this removes the dependence of this driver on the
msm_iomap.h and cpu.h mach include headers provied by MSM. This
is necessary to support single zImage work in the future and
allows us to remove cpu.h entirely and brings us closer to
removing msm_iomap.h.

Cc: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Rohit Vaswani <rvaswani@codeaurora.org>
Acked-by: Rohit Vaswani <rvaswani@codeaurora.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>