powerpc/mm: Add early_[cpu|mmu]_has_feature()

In later patches, we will be switching CPU and MMU feature checks to
use static keys.

For checks in early boot before jump label is initialized we need a
variant of [cpu|mmu]_has_feature() that doesn't use jump labels.

So create those called, unimaginatively, early_[cpu|mmu]_has_feature().

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>