Add logic to enable SAM4L clocks
Update SAM4L PLL0 logic
SAM4L:  Add DFLL0 support, add logic to set the power scaling mode, add support for RAM functions
SAM4L: Add logic to enable selected peripherals on power up; Extend configuration so that each peripheral can be selected -- even though the drivers are not yet implemented
SAM4L: Add logic to configure FLASH read mode and wait states
SM4L:  USB clock configuration and WDT register definition file
SAM4L: Add USART/UART register definition header files
SAM3U/4L changes to hide differences by clocking in those MCUs
SAM4L:  Mic fixes to get the SAM4L Xplained running.  The ostest now passes.
SAM4L:  Add an NSH configuration and C++ support
SAM4L:  Extend interrupt support for the larger number of NVIC interrupts of the SAM4L
Beginning updates of SAM3U header files o include support for the SAM4S: WDT, SUPC, EEFC, MATRIX, and PMC
SAM4S:  Add memory map and interrupt logic
Add a directory to hold configurations for the SAM4S Xplained board
SAM4S: GPIO, chip characteristics, peripheral Kconfig
SAM4S:  Add pin multiplexing definitions
SAM4S:  Add macros to manage peripheral clocks
Add configs/sam4s-xplained
Changes for a clean build of configs/sam4s-xplained
Calibrate SAM4L Xplained Pro timing loop