ARM: msm: Move io mapping prototypes to common.h

Consolidate the handful of iomapping functions into common.h so
that board files don't need to include mach/msm_iomap.h if they
don't need static virtual mapping addresses.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: David Brown <davidb@codeaurora.org>