msm: rpm-master-stat: Modify RPM master stats platform data

Currently each master stats are placed in RPM message
RAM at a fixed offset location. This can be varied across
different platforms. Hence adding  a 'master_offset'
variable to platform data. This avoids the hard coding
of offset value in rpm master stats driver.

CRs-Fixed: 517589
Change-Id: Ifb89b518930022a735495622712f694a987f47f3
Signed-off-by: Murali Nalajala <mnalajal@codeaurora.org>