apps: remove lc_open_from_mem() from plugin API

No plugin uses it and it doesn't work on hosted targets,
which limits its utility.

Change-Id: I5f29eec4dd11ffceb7be3e4d26e536483058055f

apps/plugin.c

@@ -533,7 +533,6 @@ static const struct plugin_api rockbox_api = {
     commit_discard_idcache,
 
     lc_open,
-    lc_open_from_mem,
     lc_get_header,
     lc_close,
 

apps/plugin.h

@@ -178,7 +178,7 @@ int plugin_open(const char *plugin, const char *parameter);
  * when this happens please take the opportunity to sort in
  * any new functions "waiting" at the end of the list.
  */
-#define PLUGIN_API_VERSION 275
+#define PLUGIN_API_VERSION 276
 
 /* 239 Marks the removal of ARCHOS HWCODEC and CHARCELL */
 
@@ -616,7 +616,6 @@ struct plugin_api {
 
     /* load code api for overlay */
     void* (*lc_open)(const char *filename, unsigned char *buf, size_t buf_size);
-    void* (*lc_open_from_mem)(void* addr, size_t blob_size);
     void* (*lc_get_header)(void *handle);
     void  (*lc_close)(void *handle);
 

docs/PLUGIN_API

@@ -1539,13 +1539,6 @@ void* lc_open(const char *filename, unsigned char *buf, size_t buf_size)
     \return
     \description
 
-void* lc_open_from_mem(void* addr, size_t blob_size)
-    \group load code api for overlay
-    \param addr
-    \param blob_size
-    \return
-    \description
-
 void led(bool on)
     \group misc
     \param on