powerpc/ps3: Fix hcall lv1_read_repository_node

The lv1 hcall #91 should be named lv1_read_repository_node, and
not lv1_get_repository_node_value.  Adjust the lv1 hcall table
and all calls.

Signed-off-by: Geoff Levand <geoff@infradead.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>