efibootmgr: Report the path to the device

Report the entire path to the device, rather than the the bit after /dev/
for the --esp command. Nothing in the tree depends on the output
format: Only bsdinstall's bootconfig script calls efibootmgr, and it
doesn't use the --esp/-E flag.

Sponsored by:		Netflix

usr.sbin/efibootmgr/efibootmgr.c

@@ -1052,7 +1052,7 @@ report_esp_device(bool do_dp, bool do_unix)
 		abspath[strlen(abspath) - strlen(relpath) - 1] = '\0';
 		printf("%s\n", abspath);
 	} else {
-		printf("%s\n", dev);
+		printf("/dev/%s\n", dev);
 	}
 	free(dev);
 	free(relpath);