powerpc/8xx: Fix user space TLB walk in dcbX fixup

The newly added fixup for buggy dcbX insn's has
a bug that always trigger a kernel TLB walk so a user space
dcbX insn will cause a Kernel Machine Check if it hits DTLB error.
Signed-off-by: NJoakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/head_8xx.S

@@ -542,11 +542,11 @@ DARFixed:/* Return from dcbx instruction bug workaround, r10 holds value of DAR
 FixupDAR:/* Entry point for dcbx workaround. */
 	/* fetch instruction from memory. */
 	mfspr	r10, SPRN_SRR0
+	andis.	r11, r10, 0x8000	/* Address >= 0x80000000 */
 	DO_8xx_CPU6(0x3780, r3)
 	mtspr	SPRN_MD_EPN, r10
 	mfspr	r11, SPRN_M_TWB	/* Get level 1 table entry address */
-	cmplwi	cr0, r11, 0x0800
-	blt-	3f		/* Branch if user space */
+	beq-	3f		/* Branch if user space */
 	lis	r11, (swapper_pg_dir-PAGE_OFFSET)@h
 	ori	r11, r11, (swapper_pg_dir-PAGE_OFFSET)@l
 	rlwimi	r11, r10, 32-20, 0xffc /* r11 = r11&~0xffc|(r10>>20)&0xffc */