qcacld-3.0: Replace currentOperChannel with curr_op_freq

Replace currentOperChannel with curr_op_freq in files:
lim_api.c lim_assoc_utils.c lim_ft.c

Change-Id: I2f06f0d10523fa0266509e860a13f57b5c35c0ee
CRs-Fixed: 2489616
3 files changed