bcma: add comment to bcma_chipco_gpio_control

Add description to the function.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: http://patchwork.linux-mips.org/patch/4588
Acked-by: Florian Fainelli <florian@openwrt.org>
1 file changed