microblaze: Optimize clear_vms_ums macro

We can save two instruction when MSR_VMS and MSR_UMS
are setup in one instruction.
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/kernel/entry.S

@@ -92,9 +92,7 @@
 	.endm
 
 	.macro	clear_vms_ums
-	msrclr	r11, MSR_VMS
-	nop
-	msrclr	r11, MSR_UMS
+	msrclr	r11, MSR_VMS | MSR_UMS
 	nop
 	.endm
 #else