iwl3945: fix "‘power_idx’ may be used uninitialized" warning

drivers/net/wireless/iwlwifi/iwl-3945.c: In function ‘iwl3945_txpower_set_from_eeprom’:
drivers/net/wireless/iwlwifi/iwl-3945.c:2222: warning: ‘power_idx’ may be used uninitialized in this function
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/iwlwifi/iwl-3945.c

@@ -2219,7 +2219,7 @@ int iwl3945_txpower_set_from_eeprom(struct iwl3945_priv *priv)
 		/* set tx power value for all OFDM rates */
 		for (rate_index = 0; rate_index < IWL_OFDM_RATES;
 		     rate_index++) {
-			s32 power_idx;
+			s32 uninitialized_var(power_idx);
 			int rc;
 
 			/* use channel group's clip-power table,