mm/mm_init.c: use deferred_init_mem_pfn_range_in_zone() to decide loop condition

mm/mm_init.c: use deferred_init_mem_pfn_range_in_zone() to decide loop condition

If deferred_init_mem_pfn_range_in_zone() return true, we know it finds
some range in (spfn, epfn). Then we can use it directly for the loop
condition.

Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Mike Rapoport (IBM) <rppt@kernel.org>
Link: https://lore.kernel.org/all/20240605071339.15330-1-richard.weiyang@gmail.com
Signed-off-by: Mike Rapoport (IBM) <rppt@kernel.org>