In [1] we prefixed ARC Timer functions with "arc_"
and now we need to accommodate that change in RT-Thread
accordingly.

[1] https://github.com/foss-for-synopsys-dwc-arc-processors/embarc_bsp/commit/86a03d4bf99c8afad68c4c6a5941cda7a41dd4fe

* the initial support of synopsys designware ARC processor
  using embARC_BSP, all synopsys ARC-based boards are
  supported:
  -ARC Software Development Platform
  -ARC EM Starter Kit
  -ARC EM Software Development Platform
  -ARC HS Development Kit
  -ARC IoT Development Kit

* The embARC BSP is a new generation embARC software development
  package.  ​It is designed to be the inter-layer between hardware and
  operating system. ​ BSP could hide the difference of hardware/boards,
  provide a unified interface to upper-layer.

* the initial support of synopsys MWDT toolchain.
  The DesignWare® ARC® MetaWare Development Toolkit builds upon
  a 25-year legacy of industry-leading compiler and debugger products.
  It is a complete solution that contains all the components needed to
  support the development, debugging and tuning of embedded applications
  for the DesignWare ARC processors.

* for detailed board information, pls go embarc.org.
Signed-off-by: NWatson Zeng <zhiwei@synopsys.com>