msm: rpm_stats: Update the base address to read rpm stats

Update the base address of the rpm sleep stats to match the address
being used by sleep stats driver on RPM. This change is needed to
allow reading of sleep stats from RPM MSG RAM.
Decrease the size of the MSG RAM for rpm_stats to 256 bytes as it
doesn't take more than that.

Change-Id: Ia78bf817d8278b72ee8a90cb5e0f755bec23bd3d
Signed-off-by: Anji Jonnala <anjir@codeaurora.org>