net: sparx5: fix compiletime_assert for GCC 4.9

Stephen reports sparx5 broke GCC 4.9 build.
Move the compiletime_assert() out of the static function.
Compile-tested only, no object code changes.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Fixes: f3cad261 ("net: sparx5: add hostmode with phylink support")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/microchip/sparx5/sparx5_netdev.c

@@ -13,7 +13,19 @@
  */
 #define VSTAX 73
 
-static void ifh_encode_bitfield(void *ifh, u64 value, u32 pos, u32 width)
+#define ifh_encode_bitfield(ifh, value, pos, _width)			\
+	({								\
+		u32 width = (_width);					\
+									\
+		/* Max width is 5 bytes - 40 bits. In worst case this will
+		 * spread over 6 bytes - 48 bits
+		 */							\
+		compiletime_assert(width <= 40,				\
+				   "Unsupported width, must be <= 40");	\
+		__ifh_encode_bitfield((ifh), (value), (pos), width);	\
+	})
+
+static void __ifh_encode_bitfield(void *ifh, u64 value, u32 pos, u32 width)
 {
 	u8 *ifh_hdr = ifh;
 	/* Calculate the Start IFH byte position of this IFH bit position */
@@ -22,11 +34,6 @@ static void ifh_encode_bitfield(void *ifh, u64 value, u32 pos, u32 width)
 	u32 bit  = (pos % 8);
 	u64 encode = GENMASK(bit + width - 1, bit) & (value << bit);
 
-	/* Max width is 5 bytes - 40 bits. In worst case this will
-	 * spread over 6 bytes - 48 bits
-	 */
-	compiletime_assert(width <= 40, "Unsupported width, must be <= 40");
-
 	/* The b0-b7 goes into the start IFH byte */
 	if (encode & 0xFF)
 		ifh_hdr[byte] |= (u8)((encode & 0xFF));