[POWERPC] 64K page support for kexec

This fixes a couple of kexec problems related to 64K page
support in the kernel.  kexec issues a tlbie for each pte.  The
parameters for the tlbie are the page size and the virtual address.
Support was missing for the computation of these two parameters
for 64K pages.  This adds that support.

Signed-off-by: Luke Browning <lukebrowning@us.ibm.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>