powerpc: Non relocatable system call doesn't need a trampoline

We need to use a trampoline when using LOAD_HANDLER(), because the
destination needs to be in the first 64kB. An absolute branch has
no such limitations, so just jump there.

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>