Revert "x86: use invd instead of wbinvd in real mode start code"

This reverts commit 0d67fac2.

As real hardware testing (*) shows the above mentioned commit
breaks U-Boot on it. Revert for the upcoming release. We may get
more information in the future and optimize the code accordingly.

(*) on Intel Edison board.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: fix a typo in the commit message]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>

arch/x86/cpu/start.S

@@ -50,7 +50,7 @@ _x86boot_start:
 	movl	%cr0, %eax
 	orl	$(X86_CR0_NW | X86_CR0_CD), %eax
 	movl	%eax, %cr0
-	invd
+	wbinvd
 
 	/*
 	 * Zero the BIST (Built-In Self Test) value since we don't have it.

arch/x86/cpu/start16.S

@@ -28,7 +28,7 @@ start16:
 	movl	%cr0, %eax
 	orl	$(X86_CR0_NW | X86_CR0_CD), %eax
 	movl	%eax, %cr0
-	invd
+	wbinvd
 
 	/* load the temporary Global Descriptor Table */
 data32 cs	lidt	idt_ptr