cc2540: Add support for CC2540 SoC

This patch adds the initial support for TI's CC254x System-on-Chip.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
cc2540: Add clock module support

This patch adds support for clock module to CC2540 SoC.

Since clock_wait(), clock_delay_usec() and clock_fine_max() are only
used in platform specific code, we don't implement them by now. We
might support them when they are needed.

The deprecated function clock_fine() is lacking a proper documentation
so we define it as an empty function. Some other SoC clock
implementations don't even define this function.

Moreover, clock_set_seconds(), seems not to be used by anyone in
Contiki source tree so we don't implement it.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
cc2540: Add rtimer module support

Since the SoC dependent file rtimer-arch.h is required to build
Contiki, we add the inital support for rtimer module. By now,
we use the system clock module to implement the rtimer module.
Nevertheless, the rtimer module will be properly support in future.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
cc2540mini: Initial support for CC2540 mini development kit

This patch add the initial files for supporting CC2540 mini
development kit from TI.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
cc2540mini: Add LED support

This patch adds the LED support for cc2540mini platform. The cc2540mini
platform has only two LEDs (green and red).

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>