atheros: ar2315-pci: rework the configuration access code

atheros: ar2315-pci: rework the configuration access code

Use __raw_{read,write}l accessors and use Abort interrupt to detect a
configuration space read/write errors. The second change improves errors
detection, what improves the device presence detection and helps us to
avoid following (and similar) errors:

pci 0000:00:00.2: ignoring class 0x7e0200 (doesn't match header type 02)
pci 0000:00:00.2: bridge configuration invalid ([bus 03-90]), reconfiguring
pci 0000:00:00.2: not setting up bridge for bus 0000:01

Signed-off-by: Sergey Ryazanov <ryazanov.s.a@gmail.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@42502 3c298f89-4303-0410-b956-a3cf2f4a3e73