qcacmn: Return 0 if fail to covert channel/frequency

It is easier to just compare return value of reg_freq_to_chan/
reg_chan_to_freq with 0 to check whether the channel is valid.

Change-Id: I4124cc090d31687774d8d71fee4efc822e0a6b38
CRs-Fixed: 2496010
2 files changed