kboot: Add md_addr to metadata

Save the address of where the metadata is loaded.

Sponsored by:		Netflix

stand/common/bootstrap.h

@@ -201,6 +201,7 @@ struct file_metadata
 {
 	size_t		md_size;
 	uint16_t	md_type;
+	vm_offset_t	md_addr;	/* Valid after copied to kernel space */
 	struct file_metadata *md_next;
 	char		md_data[1];	/* data are immediately appended */
 };

stand/common/modinfo.c

@@ -95,8 +95,10 @@
 #define MOD_METADATA(a, mm, c) {		\
     COPY32(MODINFO_METADATA | mm->md_type, a, c);\
     COPY32(mm->md_size, a, c);			\
-    if (c)					\
+    if (c) {					\
         archsw.arch_copyin(mm->md_data, a, mm->md_size);\
+	mm->md_addr = a;			\
+    }						\
     a += MOD_ALIGN(mm->md_size);		\
 }