powerpc/64e: remove 64s specific interrupt soft-mask code

Since the assembly soft-masking code was moved to 64e specific, there
are some 64s specific interrupt types still there. Remove them.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200915114650.3980244-4-npiggin@gmail.com