powerpc/hash: Skip non initialized page size in init_hpte_page_sizes

One of the easiest way to test config with 4K HPTE is to disable 64K hardware
page size like below.

int __init htab_dt_scan_page_sizes(unsigned long node,

 		size -= 3; prop += 3;
 		base_idx = get_idx_from_shift(base_shift);
-		if (base_idx < 0) {
+		if (base_idx < 0 || base_idx == MMU_PAGE_64K) {
 			/* skip the pte encoding also */
 			prop += lpnum * 2; size -= lpnum * 2;

But then this results in error in other part of the code such as MPSS parsing
where we look at 4K base page size and 64K actual page size support.

This patch fix MPSS parsing by ignoring the actual page sizes marked
unsupported. In reality this can happen only with a corrupt device tree. But it
is good to tighten the error check.

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