ath5k: new function for setting the antenna switch table

Collect all pieces concering the antenna switch table into one function.
Previously it was split up between ath5k_hw_reset() and
ath5k_hw_commit_eeprom_settings().

Also we need to set the antenna switch table when ath5k_hw_set_antenna_mode()
is called manually (by "iw phy0 antenna set", for example).

I'm not sure if we need to set the switchtable at the same place in
ath5k_hw_reset() as it was before - it is set later thru
ath5k_hw_set_antenna_mode() anyways - but i leave it there to avoid
problems(?).

Plus print switchtable registers in the debugfs file.

Signed-off-by: Bruno Randolf <br1@einfach.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>