arch/arm/src/tiva: Implements an EEPROM driver in compliance with MTD driver...

arch/arm/src/tiva:  Implements an EEPROM driver in compliance with MTD driver as provided by NUTTX for TM4C1294.  The EEPROM driver currently supports only two functionalities - read bytes(multiple of 4) and write bytes (multiple of 4).

Squashed commit of the following:

Author: Gregory Nutt <gnutt@nuttx.org>
    Fix some spacing
    arch/arm/src/tiva:  Verify that the EEPROM driver at least builds.
    arch/arm/src/tiva:  Move unused function added to tm4c129_syscontrol.c to tiva_eeprom.c where it is actually used.
    arch/arm/src/tiva:  Reorganize EEPROM register definitions so that the file organization is more like other platforms.
    arch/arm/src/tiva:  Trying to resolve EEPROM register addressing.  Still some issues.
    arch/arm/src/tiva:  Ran uncrustify on tiva_eeprom.c
    arch/arm/src/tiva:  EEPROM driver is a little closer to coding standard.  Still a way to go.

Author: Shirshak Sengupta <sgshirshak@gmail.com>
    arch/arm/src/tiva: Implemented EEPROM driver in compliance with MTD driver as provided by NUTTX for TM4C1294. The EEPROM driver needs to be initialized by calling the function tiva_EEPROMInit The EEPROM driver currently supports only two functionalities - read bytes(multiple of 4) and write bytes (multiple of 4). Note - Rest of the features of EEPROM will be implemented in the future.