add LittlevGL demo on stm32f746 discovery board

currently we DONOT have a 51822 xxAC(we only have xxAA of which the ram is only 16k which is too small to porting nimble, means currently the nimble ble on 51822 probably may not work). xxAC is coming soon(on EMS), I will make nimble on 51822 xxAC later.

add risc-v board Sipeed Longan Nano support

add gcc examples Makefile of tencent_cloud_sdk_mqtt

reduce two instructions in risc-v irq handler

add license for arch

Thank jiejie for contribution.

add license for kernel

Fixes to atcmd-board and gpio-board.

add gcc examples Makefile on TencentOS_tiny_EVB_MX board

risc-v add irq stack