powerpc/ps3: Rework htab code to remove ioremap

Rework the PS3 MMU hash table code to remove the need to ioremap the
hash table by using the HV calls lv1_insert_htab_entry() and
lv1_read_htab_entries().

This fixes a runtime failure on the PS3 introduced by the powerpc
ioremap_prot rework of commit a1f242ff
("powerpc ioremap_prot").

Signed-off-by: Masakazu Mokuno <mokuno@sm.sony.co.jp>
CC: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Geoff Levand <geoffrey.levand@am.sony.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>