src/include: Remove unnecessary typecast

Fix the following warning detected by checkpatch.pl:

WARNING: Unnecessary typecast of c90 int constant

TEST=Build and run on Galileo Gen2

Change-Id: I137efa55e945d1315322df2a38d70716a3807a1e
Signed-off-by: Lee Leahy <Leroy.P.Leahy@intel.com>
Reviewed-on: https://review.coreboot.org/18658
Tested-by: build bot (Jenkins)
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/src/include/swab.h b/src/include/swab.h
index a372797..7d781a0 100644
--- a/src/include/swab.h
+++ b/src/include/swab.h
@@ -25,10 +25,10 @@
 
 #define swab32(x) \
 	((unsigned int)( \
-		(((unsigned int)(x) & (unsigned int)0x000000ffUL) << 24) | \
-		(((unsigned int)(x) & (unsigned int)0x0000ff00UL) <<  8) | \
-		(((unsigned int)(x) & (unsigned int)0x00ff0000UL) >>  8) | \
-		(((unsigned int)(x) & (unsigned int)0xff000000UL) >> 24)))
+		(((unsigned int)(x) & 0x000000ffUL) << 24) | \
+		(((unsigned int)(x) & 0x0000ff00UL) <<  8) | \
+		(((unsigned int)(x) & 0x00ff0000UL) >>  8) | \
+		(((unsigned int)(x) & 0xff000000UL) >> 24)))
 
 #define swab64(x) \
 	((uint64_t)( \