[POWERPC] Use PAGE_OFFSET to tell if an address is user/kernel in SW TLB handlers

Move to using PAGE_OFFSET instead of TASK_SIZE or KERNELBASE value on
6xx/40x/44x/fsl-booke to determine if the faulting address is a kernel or
user space address.  This mimics how the macro is_kernel_addr() works.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index e312824..cfefc2d 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -289,7 +289,7 @@
 	/* If we are faulting a kernel address, we have to use the
 	 * kernel page tables.
 	 */
-	lis	r11, TASK_SIZE@h
+	lis	r11, PAGE_OFFSET@h
 	cmplw	r10, r11
 	blt+	3f
 	lis	r11, swapper_pg_dir@h
@@ -481,7 +481,7 @@
 	/* If we are faulting a kernel address, we have to use the
 	 * kernel page tables.
 	 */
-	lis	r11, TASK_SIZE@h
+	lis	r11, PAGE_OFFSET@h
 	cmplw	r10, r11
 	blt+	3f
 	lis	r11, swapper_pg_dir@h
@@ -581,7 +581,7 @@
 	/* If we are faulting a kernel address, we have to use the
 	 * kernel page tables.
 	 */
-	lis	r11, TASK_SIZE@h
+	lis	r11, PAGE_OFFSET@h
 	cmplw	r10, r11
 	blt+	3f
 	lis	r11, swapper_pg_dir@h