[BSP] Port to NuMicro M051 Series support for Nuvoton corp and fix compile warning

it works fine on Nu-Tiny-SDK.

1. adapt to M052xDN/xDE, M054xDN/xDE, M058xDN/xDE, M0516/xDN/xDE.
2. support heap memory management.
3. fix variable "c" was declared but never referenced,  when RT_USING_CONSOLE is disable.