qcacld-3.0: Convert CSR legacy channel ID usage

1) Change the following functions to make them use channel
   frequencies intead of channel IDs:

   csr_process_roam_sync_callback
   csr_save_to_channel_power2_g_5_g
   csr_save_tx_power_to_cfg

2) Remove some local variable and code within function
   csr_save_tx_power_to_cfg as they're not used.

3) Retain the code for channel ID utilization within
   csr_get_channel_power_info as they're used to
   indicate diag info to upper layer apps.

Change-Id: Ib294fd04f770c008afaa0049fb1951aa912caf34
CRs-Fixed: 2573403
2 files changed