[MIPS] Do not count pages in holes with sparsemem

[MIPS] Do not count pages in holes with sparsemem

With some memory model other than FLATMEM, the single node can
contains some holes so there might be many invalid pages.  For
example, with two 256M memory and one 256M hole, some variables
(num_physpage, totalpages, nr_kernel_pages, nr_all_pages, etc.) will
indicate that there are 768MB on this system.  This is not desired
because, for example, alloc_large_system_hash() allocates too many
entries.

Use free_area_init_node() with counted zholes_size[] instead of
free_area_init().

For num_physpages, use number of ram pages instead of max_low_pfn.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>