MIPS: MTX-1: Fix PCI on the MeshCube and related boards

MIPS: MTX-1: Fix PCI on the MeshCube and related boards

This patch fixes a regression introduced by commit "MIPS: Alchemy: MTX-1:
Use linux gpio api." (bb706b28bbd647c2fd7f22d6bf03a18b9552be05) which broke
PCI bus operation. The problem is caused by alchemy_gpio2_enable() which
resets the GPIO2 block. Two PCI signals (PCI_SERR and PCI_RST) are connected
to GPIO2 and they obviously do not to like the reset. Since GPIO2 is
correctly initialized by the boot monitor (YAMON) it is not necessary to
call this function, so just remove it.

Also replace gpio_set_value() with alchemy_gpio_set_value() to avoid
problems in case gpiolib gets initialized after PCI. And since alchemy
gpio_set_value() calls au_sync() we don't have to au_sync() again later.

Signed-off-by: Bruno Randolf <br1@einfach.org>
To: linux-mips@linux-mips.org
To: manuel.lauss@googlemail.com
Patchwork: https://patchwork.linux-mips.org/patch/1448/
Tested-by: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>