link_elf_obj: Colour VM objects

This will cause the VM to back sufficiently large .text sections, such
as those in zfs.ko or amdgpu.ko on amd64, with superpage mappings when
possible.

Reviewed by:	alc, kib
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D26802

sys/kern/link_elf_obj.c

@@ -914,6 +914,9 @@ link_elf_load_file(linker_class_t cls, const char *filename,
 		error = ENOMEM;
 		goto out;
 	}
+#if VM_NRESERVLEVEL > 0
+	vm_object_color(ef->object, 0);
+#endif
 
 	/*
 	 * In order to satisfy amd64's architectural requirements on the