1. Add EFM32 development kit support
2. Add USART sync mode (SPI) support
3. Add SPI Flash device (ST M25PX16) driver and demo application

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1401 bbd45198-f89e-11dd-88c7-29a3b14d5316

 - New branch for Energy Micro's MCUs (http://energymicro.com/).
 - Target board: FM32 Gecko Starter Kit (http://www.energymicro.com/tools)

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@1274 bbd45198-f89e-11dd-88c7-29a3b14d5316