Added linker files for TM4C123xC3, TM4C123xD5, TM4C123xE6 and TM4C123xH6.
Added cmparams.h for TM4C123x.
Added board.c, board.h and board.mk for the Tiva Launchpad board.
Added port_tm4c123x.mk file for ChibiOS/RT.
Added hal, pal, serial and st low level drivers, custom tm4c123x CMSIS header file, tiva_isr, tiva_registry and platform.mk files.
Added demo project for the Tiva C Series TM4C123G Launchpad and updated the README file with the directory structure.
Merge branch 'feature/Add_files' into develop