powerpc/32s: Use mmu_has_feature(MMU_FTR_HPTE_TABLE) instead of checking Hash var

We now have an early hash table on hash MMU, so no need to check
Hash var to know if the Hash table is set of not.

Use mmu_has_feature(MMU_FTR_HPTE_TABLE) instead. This will allow
optimisation via jump_label.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/f1766631a9e014b6433f1a3c12c726ddfce34220.1603348103.git.christophe.leroy@csgroup.eu