powerpc/32: Fix boot failure on non 6xx platforms

Commit d300627c ("powerpc/6xx: Handle DABR match before calling
do_page_fault") breaks non 6xx platforms.

  Failed to execute /init (error -14)
  Starting init: /bin/sh exists but couldn't execute it (error -14)
  Kernel panic - not syncing: No working init found.  Try passing init= ...
  CPU: 0 PID: 1 Comm: init Not tainted 4.13.0-rc3-s3k-dev-00143-g7aa62e972a56 #56
  Call Trace:
    panic+0x108/0x250 (unreliable)
    rootfs_mount+0x0/0x58
    ret_from_kernel_thread+0x5c/0x64
  Rebooting in 180 seconds..

This is because in handle_page_fault(), the call to do_page_fault() has been
mistakenly enclosed inside an #ifdef CONFIG_6xx

Fixes: d300627c ("powerpc/6xx: Handle DABR match before calling do_page_fault")
Brown-paper-bag-to-be-worn-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/entry_32.S

@@ -586,11 +586,11 @@ ppc_swapcontext:
 handle_page_fault:
 	stw	r4,_DAR(r1)
 	addi	r3,r1,STACK_FRAME_OVERHEAD
-	andis.  r0,r5,DSISR_DABRMATCH@h
 #ifdef CONFIG_6xx
+	andis.  r0,r5,DSISR_DABRMATCH@h
 	bne-    handle_dabr_fault
-	bl	do_page_fault
 #endif
+	bl	do_page_fault
 	cmpwi	r3,0
 	beq+	ret_from_except
 	SAVE_NVGPRS(r1)