MIPS: BCM47XX: Enable USB power on Netgear WNDR3400v3

MIPS: BCM47XX: Enable USB power on Netgear WNDR3400v3

[ Upstream commit feef7918667b84f9d5653c501542dd8d84ae32af ]

Setting GPIO 21 high seems to be required to enable power to USB ports
on the WNDR3400v3. As there is already similar code for WNR3500L,
make the existing USB power GPIO code generic and use that.

Signed-off-by: Tuomas Tynkkynen <tuomas.tynkkynen@iki.fi>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/20259/
Cc: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>