Replaced the nops after starting the gpio peripheral clocks with a busy wait until all GPIO peripherals are ready.
Added Sub-Family identifier for TM4C123x devices.
Updated gpt_lld, i2c_lld, pal_lld, pwm_lld, serial_lld, hal_lld register access to the changed peripheral register structures.
Replaced old interrupt numbers from tm4c123x.h and tm4c129x.h in serial_lld.c with the new interrupt number defines from tiva_isr.h.