defconfig: arm64: increase log buffer size by 96KB

Due to kernel log flooding during the boot, the first message
might be missing. So increase the log buffer size by adding
cpu extra buffer.

Change-Id: I246e2d8f994b35a2dfe4e29a8daf4f5496390eaa
Signed-off-by: Se Wang (Patrick) Oh <sewango@codeaurora.org>