UART baud rate is main clock (MCK) divided by CR*16.
The MCK values are chosen >= 48 MHz and <= 64 MHz to have a near
integer value CR for a baud rate of 921600 bps.
The end MCK frequency between simtrace and qmod differ slightly
but are close to 58 MHz.
Change-Id: Iaa4a97fc68494c93b9d128503515d88049de506c
Sometimes there is some leakage current via some I/O that's sufficient
to power up the SAM3S. Use the supply monitor to make sure the CPU
will be reset (and kept in reset) if the supply voltage is below 3.0V.
This way we can easily check with 'diff' for differences in our code and
Atmel softpack. Also, this layout is more suitable for building various
different firmware images (e.g. factory-test, dfu-loader, main
application) for a variety of different boards (simtrace, owhw, qmod).
