powerpc/64: switch asm helpers from GOT to TOC relative addressing

There is no need to use GOT addressing within the kernel.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220926034057.2360083-4-npiggin@gmail.com