[PATCH] powerpc: Separate usage of KERNELBASE and PAGE_OFFSET

This patch separates usage of KERNELBASE and PAGE_OFFSET. I haven't
looked at any of the PPC32 code, if we ever want to support Kdump on
PPC we'll have to do another audit, ditto for iSeries.

This patch makes PAGE_OFFSET the constant, it'll always be 0xC * 1
gazillion for 64-bit.

To get a physical address from a virtual one you subtract PAGE_OFFSET,
_not_ KERNELBASE.

KERNELBASE is the virtual address of the start of the kernel, it's
often the same as PAGE_OFFSET, but _might not be_.

If you want to know something's offset from the start of the kernel
you should subtract KERNELBASE.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/btext.c

@@ -60,7 +60,7 @@ int force_printk_to_btext = 0;
  *
  * The display is mapped to virtual address 0xD0000000, rather
  * than 1:1, because some some CHRP machines put the frame buffer
- * in the region starting at 0xC0000000 (KERNELBASE).
+ * in the region starting at 0xC0000000 (PAGE_OFFSET).
  * This mapping is temporary and will disappear as soon as the
  * setup done by MMU_Init() is applied.
  *
@@ -71,7 +71,7 @@ int force_printk_to_btext = 0;
  */
 void __init btext_prepare_BAT(void)
 {
-	unsigned long vaddr = KERNELBASE + 0x10000000;
+	unsigned long vaddr = PAGE_OFFSET + 0x10000000;
 	unsigned long addr;
 	unsigned long lowbits;