powerpc/mm: Standardise pte_update() prototype between PPC32 and PPC64

PPC64 takes 3 additional parameters compared to PPC32:
- mm
- address
- huge

These 3 parameters will be needed in order to perform different
action depending on the page size on the 8xx.

Make pte_update() prototype identical for PPC32 and PPC64.

This allows dropping an #ifdef in huge_ptep_get_and_clear().

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/38111acf6841047a8addde37c63e92d611ee38c2.1589866984.git.christophe.leroy@csgroup.eu