s390/mm: avoid trimming to MAX_ORDER

Trimming to MAX_ORDER was originally done in order to avoid to set
HOLES_IN_ZONE, which in turn would enable a quite expensive
pfn_valid() check. pfn_valid() however only checks if a struct page
exists for a given pfn.

With sparsemen vmemmap there are always struct pages, since memmaps
are allocated for whole sections. Therefore remove the HOLES_IN_ZONE
comment and the trimming.
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/kernel/setup.c

@@ -1126,14 +1126,6 @@ void __init setup_arch(char **cmdline_p)
 	free_mem_detect_info();
 	remove_oldmem();
 
-	/*
-	 * Make sure all chunks are MAX_ORDER aligned so we don't need the
-	 * extra checks that HOLES_IN_ZONE would require.
-	 *
-	 * Is this still required?
-	 */
-	memblock_trim_memory(1UL << (MAX_ORDER - 1 + PAGE_SHIFT));
-
 	if (is_prot_virt_host())
 		setup_uv();
 	setup_memory_end();