msm: Makefile: add platsmp build support for 8226

The 8910 platsmp file will be used for 8226 as well. Add support
to compile this file for both targets using a common CONFIG option.

Change-Id: I0595991828f61d849facb8bc7069310f0c8d8f3a
Signed-off-by: Syed Rameez Mustafa <rameezmustafa@codeaurora.org>