msm: 9615: Update rpm stats base address

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: I37f394940ad4f9104a7ec68c835593573f5ea2f4
Signed-off-by: Anji Jonnala <anjir@codeaurora.org>