brcmfmac: fix generation of the p2p related mac addresses

The driver determines the P2P interface address and device
address from the primary mac address. However, the function
used an invalid input. This caused a mac address mismatch
between firmware and driver. This was hidden because the
brcmf_if_add() function corrected the error upon receiving
the IF_ADD event from firmware.

Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Hante Meuleman <meuleman@broadcom.com>
Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>