MIPS: init: Ensure reserved memory regions are not added to bootmem

Memories managed through boot_mem_map are generally expected to define
non-crossing areas. However, if part of a larger memory block is marked
as reserved, it would still be added to bootmem allocator as an
available block and could end up being overwritten by the allocator.

Prevent this by explicitly marking the memory as reserved it if exists
in the range used by bootmem allocator.
Signed-off-by: NMarcin Nowakowski <marcin.nowakowski@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/14608/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

arch/mips/kernel/setup.c

@@ -483,6 +483,10 @@ static void __init bootmem_init(void)
 			continue;
 		default:
 			/* Not usable memory */
+			if (start > min_low_pfn && end < max_low_pfn)
+				reserve_bootmem(boot_mem_map.map[i].addr,
+						boot_mem_map.map[i].size,
+						BOOTMEM_DEFAULT);
 			continue;
 		}