get_macaddrs: fix softmac file permissions

CM10.2 is stricter than before. Updated permissions to fix softmac
support in ath6kl driver.

Change-Id: I0fd17849c193ec7abbccf8dc541d686fc63a9d8e
(cherry picked from commit 2d31d822ffb6fb0dd99d166a52bbf7f647872236)