remove DefaultDevice's UI subclass

RecoveryUI (which is the superclass of ScreenRecoveryUI), provides a
basic CheckKey method that is useful for devices that have KEY_POWER,
KEY_VOLUMEUP, and KEY_VOLUMEDOWN.  Stop overriding it with a less
featureful method; with this no recovery UI customization is needed
for most handheld devices (phones, tablets, etc.).

Change-Id: I7d57cfaaef79afea8af4fc3dbc570afc61aeb5bc
diff --git a/ui.cpp b/ui.cpp
index 67a2500..091012f 100644
--- a/ui.cpp
+++ b/ui.cpp
@@ -276,7 +276,7 @@
 // - Press power seven times in a row to reboot.
 // - Alternate vol-up and vol-down seven times to mount /system.
 RecoveryUI::KeyAction RecoveryUI::CheckKey(int key) {
-    if (IsKeyPressed(KEY_POWER) && key == KEY_VOLUMEUP) {
+    if ((IsKeyPressed(KEY_POWER) && key == KEY_VOLUMEUP) || key == KEY_HOME) {
         return TOGGLE;
     }