ar71xx: add mc-mac1200r to do_load_ath10k_board_bin()

This patch adds the mc-mac1200r target to do_load_ath10k_board_bin() in
target/linux/ar71xx/base-files/lib/preinit/81_load_ath10k_board_bin to load the
ath10k radio MAC address from the EEPROM in MERCURY MAC1200R devices

Signed-off-by: Roger Pueyo Centelles <roger.pueyo@guifi.net>

SVN-Revision: 44375