soc: qcom: Add support to dump initial bootup logs

Add support to dump initial dmesg buffer into a
buffer available in minidump and fulldump.

Make logs copying from log_buf at configurable.
This is required to avoid memory sensitive target
from using this.

Change-Id: I7e4d0ddc138ff09c9cbe7679db5e790cdaf1db5c
Signed-off-by: Prateek Sood <prsood@codeaurora.org>