ath9k: add support for endian swap of eeprom from platform data

On some devices (especially little-endian ones), the flash EEPROM data
has a different endian, which needs to be detected.
Add a flag to the platform data to allow overriding that behavior

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/include/linux/ath9k_platform.h b/include/linux/ath9k_platform.h
index a495a95..4350165 100644
--- a/include/linux/ath9k_platform.h
+++ b/include/linux/ath9k_platform.h
@@ -31,6 +31,7 @@
 	u32 gpio_mask;
 	u32 gpio_val;
 
+	bool endian_check;
 	bool is_clk_25mhz;
 	bool tx_gain_buffalo;