softap: sscanf sanity check for SoftAP service

The sscanf return value is verified whether the three channel
variables, i.e. start channel, end channel and channel band,
are properly updated. If malformed input is given to sscanf, then
these variables may not properly updated. To provide validation
of input,  verifying that sscanf returned a correct value of 3.

Change-Id: Ibd185e7a0ffcf5803927990531fc33f0e8977cc9
CRs-fixed: 554349
qcom: softap: Fix potential string null termination and buffer overflow

Fix potential string null termination and buffer overflow

Change-Id: I05e28b30a4e3134625d20fb5591b239ea4b9f3a4
CRs-fixed: 554078
wlan: Don't overwrite the channel configured in hostapd.conf

When SAP is turned on through GUI, hostapd.conf file
will be overwritten by the framework parameters.Since
in Kit-Kat framework,channel value is hard coded to 6,
same is getting over written whenever we turn on SAP
through GUI, this will cause SAP to come up always on
channel 6.
To mitigate this issue, avoid overwriting the channel
parameter in hostap.conf file by ignoring the channel
parameter from the framework.

Change-Id: I4d87cf70868ad705f63211b2bd10ac2a67646d09
CRs-Fixed: 584112