[IA64] fix csum_ipv6_magic()

The 32-bit parameters (len and csum) of csum_ipv6_magic() are passed in 64-bit
registers in2 and in4. The high order 32 bits of the registers were never
cleared, and garbage was sometimes calculated into the checksum.

Fix this by clearing the high order 32 bits of these registers.
Signed-off-by: Jiri Bohac <jbohac@suse.cz>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/lib/ip_fast_csum.S

@@ -96,20 +96,22 @@ END(ip_fast_csum)
 GLOBAL_ENTRY(csum_ipv6_magic)
 	ld4	r20=[in0],4
 	ld4	r21=[in1],4
-	dep	r15=in3,in2,32,16
+	zxt4	in2=in2
 	;;
 	ld4	r22=[in0],4
 	ld4	r23=[in1],4
-	mux1	r15=r15,@rev
+	dep	r15=in3,in2,32,16
 	;;
 	ld4	r24=[in0],4
 	ld4	r25=[in1],4
-	shr.u	r15=r15,16
+	mux1	r15=r15,@rev
 	add	r16=r20,r21
 	add	r17=r22,r23
+	zxt4	in4=in4
 	;;
 	ld4	r26=[in0],4
 	ld4	r27=[in1],4
+	shr.u	r15=r15,16
 	add	r18=r24,r25
 	add	r8=r16,r17
 	;;