Fix littlevgl link error issues (#1006)

The littlevgl library had changed its name and domain to [LVGL](https://lvgl.io).
See https://blog.lvgl.io/2020-06-01/announcement
We change some names and links accordingly.

Also remove the cloning for tlsf library as it isn't used now.

samples/littlevgl/build.sh

@@ -34,7 +34,7 @@ mkdir ${OUT_DIR}
 cd ${BUILD_DIR}
 if [ ! -d "lvgl" ]; then
         echo "starting download lvgl for v5.3 ..."
-        git clone https://github.com/littlevgl/lvgl.git --branch v5.3
+        git clone https://github.com/lvgl/lvgl.git --branch v5.3
         if [ $? != 0 ];then
             echo "download lvgl repo failed: $?\n"
             exit 2

samples/littlevgl/vgl-native-ui-app/CMakeLists.txt.in

@@ -7,7 +7,7 @@ project(lvgl_download NONE)
 
 include(ExternalProject)
 ExternalProject_Add(${lv_name}
-    GIT_REPOSITORY https://github.com/littlevgl/lvgl.git
+    GIT_REPOSITORY https://github.com/lvgl/lvgl.git
     GIT_TAG        v5.3
     BINARY_DIR     ""
     SOURCE_DIR            "${CMAKE_CURRENT_BINARY_DIR}/../build/lvgl"

samples/simple/build.sh

@@ -95,10 +95,6 @@ mkdir ${OUT_DIR}
 mkdir ${OUT_DIR}/wasm-apps
 
 cd ${WAMR_DIR}/core/shared/mem-alloc
-if [ ! -d "tlsf" ]; then
-    git clone https://github.com/mattconte/tlsf
-fi
-
 
 PROFILE="simple-$PROFILE"