msm: Refactor cpu_is macros into SoC classes

Refactor common combinations of cpu_is macros into logical
SoC class macros to reduce the maintenance burden of
implementing support for additional product variants.

Change-Id: I6472eb70fa43e1217ff3ebb3643288196b9864b5
Signed-off-by: Stepan Moskovchenko <stepanm@codeaurora.org>