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>
cc2540mini: Add putchar()

Each platform should define its own putchar() according to platform
characteristics.

Since cc2540mini porting is in early stage, we define an empty
putchar() so we are able to compile hello-world example.

Signed-off-by: Andre Guedes <andre.guedes@openbossa.org>
Add cscope files to .gitignore

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