Remove read-only flag from U-boot environment partition for Netgear
WNDR3700 v1 and v2 so u-boot-envtools can modify data there.
Signed-off-by: Michal Cieslakiewicz <michal.cieslakiewicz@wp.pl>
(cherry picked from commit 6227c8d1bf41739586969c3102897a7ba179114d)