brcm63xx: 3.14: fix ath9k_pci_fixup

Since kernel commit 928bea964827 ("PCI: Delay enabling bridges until
they're needed"), pci fixups are run with bridges (e.g. the pcie port)
disabled.

This causses hangs when ath9k_pci_fixup tries to manually enable the
device to apply the register fixups.

Fix this by enabling any parent bridges before trying to access the
device itself.

Fixes boot on DSL-274XB rev F1.

Reported-by: Matteo Croce <matteo@openwrt.org>
Signed-off-by: Jonas Gorski <jogo@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@41856 3c298f89-4303-0410-b956-a3cf2f4a3e73