s4-common: set the bootloader msg offset

HTC offsets the bootloader message to 0x800 (2048) in /misc. This
prevents overwriting other stored variables in misc, such as the most
recently installed stock OS version.

Change-Id: I8499c9a3786820d105cc79968f010e16466124b3
Merge branch 'cm-11.0' into kk_mkt