qcom: common_log: make dump registration as async

In common log buf registration, finding log_buf symbols
takes more time and it stalls kernel booting.

So make log buf and other subsystem registration as async
task to optimize boot time.

Change-Id: I2c771195cc07c57a6e03a169b1d12fefb5560e17
Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>