powerpc/mm: Fix _PAGE_COHERENT support on classic ppc32 HW

The following commit:

commit 64b3d0e8122b422e879b23d42f9e0e8efbbf9744
Author: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Date:   Thu Dec 18 19:13:51 2008 +0000

    powerpc/mm: Rework usage of _PAGE_COHERENT/NO_CACHE/GUARDED

broke setting of the _PAGE_COHERENT bit in the PPC HW PTE.  Since we now
actually set _PAGE_COHERENT in the Linux PTE we shouldn't be clearing it
out before we propogate it to the PPC HW PTE.

Reported-by: Martyn Welch <martyn.welch@gefanuc.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/hash_low_32.S

@@ -320,7 +320,7 @@ _GLOBAL(create_hpte)
 	and	r8,r8,r0		/* writable if _RW & _DIRTY */
 	rlwimi	r5,r5,32-1,30,30	/* _PAGE_USER -> PP msb */
 	rlwimi	r5,r5,32-2,31,31	/* _PAGE_USER -> PP lsb */
-	ori	r8,r8,0xe14		/* clear out reserved bits and M */
+	ori	r8,r8,0xe04		/* clear out reserved bits */
 	andc	r8,r5,r8		/* PP = user? (rw&dirty? 2: 3): 0 */
 BEGIN_FTR_SECTION
 	rlwinm	r8,r8,0,~_PAGE_COHERENT	/* clear M (coherence not required) */