ath9k: break up hw initialization into a few more helpers

This makes reading the hardware initialization process
easier to understand. The new helpers added are:

ath9k_hw_init_cal_settings()
ath9k_hw_init_mode_regs()
ath9k_hw_init_mode_gain_regs()
ath9k_hw_init_11a_eeprom_fix()

This patch has no functional changes.

Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>