amd64: parse_memmap(): Move comment about size at proper place

While here, declare 'size' only in the relevant block.

No functional change (intended).

MFC after:      1 week
Sponsored by:   The FreeBSD Foundation

sys/amd64/amd64/machdep.c

@@ -827,15 +827,6 @@ native_parse_memmap(vm_paddr_t *physmap, int *physmap_idx)
 {
 	struct bios_smap *smap;
 	struct efi_map_header *efihdr;
-	u_int32_t size;
-
-	/*
-	 * Memory map from INT 15:E820.
-	 *
-	 * subr_module.c says:
-	 * "Consumer may safely assume that size value precedes data."
-	 * ie: an int32_t immediately precedes smap.
-	 */
 
 	efihdr = (struct efi_map_header *)preload_search_info(preload_kmdp,
 	    MODINFO_METADATA | MODINFOMD_EFI_MAP);
@@ -848,7 +839,15 @@ native_parse_memmap(vm_paddr_t *physmap, int *physmap_idx)
 		add_efi_map_entries(efihdr, physmap, physmap_idx);
 		strlcpy(bootmethod, "UEFI", sizeof(bootmethod));
 	} else {
-		size = *((u_int32_t *)smap - 1);
+		/*
+		 * Memory map from INT 15:E820.
+		 *
+		 * subr_module.c says:
+		 * "Consumer may safely assume that size value precedes data."
+		 * ie: an int32_t immediately precedes smap.
+		 */
+		u_int32_t size = *((u_int32_t *)smap - 1);
+
 		bios_add_smap_entries(smap, size, physmap, physmap_idx);
 		strlcpy(bootmethod, "BIOS", sizeof(bootmethod));
 	}