wifi: rt2x00: check retval for of_get_mac_address

wifi: rt2x00: check retval for of_get_mac_address

of_get_mac_address can return -EPROBE_DEFER when nvmem is not probed yet
for whatever reason. In this case, nvmem mac assignments will not work.

Based on the function path, this change only has effect for rt2800soc.c
and rt2800pci.c. The former tends to use nvmem for assignments.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
Acked-by: Stanislaw Gruszka <stf_xl@wp.pl>
Link: https://patch.msgid.link/20251014050833.46377-1-rosenp@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>