mach-msm: common_log: add common log support

Add common log code to register kernel log buffer address with
the memory dump driver so that the __log_buf can be collected from
ramdumps without the need of an external System.map file.

Change-Id: I0652e9aaafaea2d5bbddf33da53acd48411a4520
Signed-off-by: Jin Wu <jinw@codeaurora.org>