don't say "install complete" when it really isn't

Change the recovery UI so that when there is a hboot or radio update
pending (which the user most do a home+back reboot to actually
install), the UI tells them so, instead of saying "Install from sdcard
complete."
diff --git a/firmware.h b/firmware.h
index f3f7aab..aeb8f97 100644
--- a/firmware.h
+++ b/firmware.h
@@ -23,6 +23,9 @@
  */
 int remember_firmware_update(const char *type, const char *data, int length);
 
+/* Returns true if a firmware update has been saved. */
+int firmware_update_pending();
+
 /* If an update was saved, reboot into the bootloader now to install it.
  * Returns 0 if no radio image was defined, nonzero on error,
  * doesn't return at all on success...