qcacld-3.0: Limit the number of times get_tx_power can come

Currently in the driver, there is no limit on how many number of times
get_tx_power can be requested by the userspace. This can lead to
potential issues where the firmware crashes due to excessive stats
request.

Add a time based rate limiting logic wherein the function call only
sends request to the firmware once in three seconds. In other cases, it
returns the cached value present in the adapter.

Change-Id: I65f23135d88c66e6438484715dafce3def14ddb3
CRs-Fixed: 2717633
5 files changed