icnss: fix the memory and kernel info leak due to the race condition

The icnss register read/write debugfs entry can be accessed by
multiple user space thread. Memory allocation and deallocation
in the register read/write file operation leads to potential
memory leak during concurrency access of debugfs device file.

Add protection to avoid the memory leak and kernel information
leak due to the race condition in the register read/write ops.

CRs-Fixed: 2012572
Change-Id: I22c6af9a396c0df4e68f75702fc68a5dff5af032
Signed-off-by: Sarada Prasanna Garnayak <sgarna@codeaurora.org>