AI 144070: Add an option to wipe cache (only) to the recovery menu.

Automated import of CL 144070
diff --git a/recovery.c b/recovery.c
index 221ee29..a0bae97 100644
--- a/recovery.c
+++ b/recovery.c
@@ -302,9 +302,11 @@
 #define ITEM_REBOOT        0
 #define ITEM_APPLY_SDCARD  1
 #define ITEM_WIPE_DATA     2
+#define ITEM_WIPE_CACHE    3
     char* items[] = { "reboot system now [Home+Back]",
                       "apply sdcard:update.zip [Alt+S]",
                       "wipe data/factory reset [Alt+W]",
+                      "wipe cache partition",
                       NULL };
 
     ui_start_menu(headers, items);
@@ -357,6 +359,13 @@
                     if (!ui_text_visible()) return;
                     break;
 
+                case ITEM_WIPE_CACHE:
+                    ui_print("\n-- Wiping cache...\n");
+                    erase_root("CACHE:");
+                    ui_print("Cache wipe complete.\n");
+                    if (!ui_text_visible()) return;
+                    break;
+
                 case ITEM_APPLY_SDCARD:
                     ui_print("\n-- Install from sdcard...\n");
                     int status = install_package(SDCARD_PACKAGE_FILE);