msm: rpm: remove the sanity check in rpm log

On 8960 it is observed that head and tail of rpm
circular buffer is not updated properly which is preventing
reading the RPM log through adb.

CRs-fixed: 365071
Change-Id: If24b7fb29fce14dccc24dbcdbe3513d22d94a298
Signed-off-by: Anji Jonnala <anjir@codeaurora.org>