ath9k_hw: move LowPower array writes to ar9003_hw_configpcipowersave()

The LowPower array writes disables the PLL when ASPM is enabled.
The host driver makes quite a few calls to ath9k_hw_configpcipowersave()
and these same calls also need to ensure the PLL is off when they issue
it.

Cc: Aeolus Yang <aeolus.yang@atheros.com>
Cc: Madhan Jaganathan <madhan.jaganathan@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>