soc: qcom: common_log: Fix a memory leak in common_log driver

Fix the memory leak in common_log_register_log_buf() function
when registering log_first_idx with the memory with dump v2 driver.
Also use kmemleak_not_leak when msm_dump_data_register() calls
are successful to ensure that kmemleak doesn't report it as a memory
leak.

CRs-Fixed: 832905
Change-Id: I36eaeebf821f64dd7503ec823aca3c7aec846bd0
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>