ath: Fix uninitialized variable warnings

Fixes 'make -j24 CONFIG_DEBUG_SECTION_MISMATCH=y' warning:

drivers/net/wireless/ath/ath9k/eeprom_4k.c: In function ‘ath9k_hw_get_4k_gain_boundaries_pdadcs.clone.1’:
drivers/net/wireless/ath/ath9k/eeprom_4k.c:311: error: ‘minPwrT4’ may be used uninitialized in this function
drivers/net/wireless/ath/ath9k/eeprom_9287.c: In function ‘ath9k_hw_get_AR9287_gain_boundaries_pdadcs’:
drivers/net/wireless/ath/ath9k/eeprom_9287.c:302: error: ‘minPwrT4’ may be used uninitialized in this function
drivers/net/wireless/ath/ath9k/eeprom_def.c: In function ‘ath9k_hw_get_def_gain_boundaries_pdadcs.clone.0’:
drivers/net/wireless/ath/ath9k/eeprom_def.c:679: error: ‘minPwrT4’ may be used uninitialized in this function

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>