powerpc/mm: Update the HID bit when switching from radix to hash

Power9 DD1 requires to update the hid0 register when switching from
hash to radix.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Acked-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>