x86, boot: Simplify setting of the PAE bit

A single 'movl' is shorter than the 'xorl'-'orl' pair.
No change in behaviour.
Signed-off-by: NAlexander Potashev <aspotashev@gmail.com>
LKML-Reference: <1256341043-4928-1-git-send-email-aspotashev@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

arch/x86/boot/compressed/head_64.S

@@ -107,8 +107,7 @@ ENTRY(startup_32)
 	lgdt	gdt(%ebp)
 
 	/* Enable PAE mode */
-	xorl	%eax, %eax
-	orl	$(X86_CR4_PAE), %eax
+	movl	$(X86_CR4_PAE), %eax
 	movl	%eax, %cr4
 
  /*