staging:rtl8188eu: Fix sparse warning cast to restricted __le16

This patch fixes the following sparse warnings:

  CHECK   drivers/staging/rtl8188eu/hal/fw.c
drivers/staging/rtl8188eu/hal/fw.c:219:13: warning: cast to restricted __le16
drivers/staging/rtl8188eu/hal/fw.c:219:13: warning: cast to restricted __le16
drivers/staging/rtl8188eu/hal/fw.c:219:13: warning: cast to restricted __le16
drivers/staging/rtl8188eu/hal/fw.c:219:13: warning: cast to restricted __le16

by changing the signature from 'u16' to '__le16'.
Signed-off-by: Tobenna P. Igwe <ptigwe@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/include/fw.h

@@ -36,7 +36,7 @@
 #define FW_8192C_POLLING_DELAY		5
 
 struct rtl92c_firmware_header {
-	u16 signature;
+	__le16 signature;
 	u8 category;
 	u8 function;
 	u16 version;