ath5k:Remove __raw_read and __raw_write

By swithing from our __raw_read and __raw_write functions to ioread32 and iowrite32,
benchmarks on my desk with iperf went from 11MBps to 18.1MBps using the AHB bus
on an EnGenius ECB3500 running OpenWRT.

Signed-off-by: Jonathan Bither <jonbither@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>