p2p: use calloc to ensure the zero-terminator

The fequency parameter of scan function is a list.
The last one must be zere to indicate the end of the list.

Bug: 130624119
Test: CtsVerifier - WiFi Direct fixed frequency test
Change-Id: Ic25a95cec97ffa1be755e81d233c1aac3b3a4634
1 file changed