Updated General Purpose Timer class.
Mutex replaced with spinlock.
Updated spinlock usage in classes.
Renamed Gpdma to GpDma, updated SerialDma class.
Fixes in Interface, Timer, Uart, SdioSpi.
* Fixed baud rate setup for UART.
* Removed callback and blocking mode from current SdioSpi implementation.
* IF_LOCK, IF_UNLOCK renamed to IF_ACQUIRE, IF_RELEASE.
* Do not clear enable bit in GP Timer initialization.
* Fixed UART rate setup in SerialDma.
Minor changes and fixes in code style.