board/ti/dra7xx: add support for parallel NAND

board/ti/dra7xx: add support for parallel NAND

This patch adds support for x16 NAND device (MT29F2G16AAD) connected to GPMC
chip-select[0] on DRA7xx EVM.
As GPMC pins are shared by multiple devices, so in addition to this patch
following board settings are required for NAND device detection [1]:

  SW5.9 (GPMC_WPN)   = OFF (logic-1)
  SW5.1 (NAND_BOOTn) = ON  (logic-0) /* Active-low */
  SW5.2 (NOR_BOOTn)  = OFF (logic-1)
  SW5.3 (eMMC_BOOTn) = OFF (logic-1)
  SW5.4 (QSPI_BOOTn) = OFF (logic-1)

And also set appropriate SYSBOOT configurations
  SW2.1 (SYSBOOT[0]) = ON  (logic-1) /* selects NAND Boot */
  SW2.2 (SYSBOOT[1]) = OFF (logic-0) /* selects NAND Boot */
  SW2.3 (SYSBOOT[2]) = OFF (logic-0) /* selects NAND Boot */
  SW2.4 (SYSBOOT[3]) = OFF (logic-0) /* selects NAND Boot */
  SW2.5 (SYSBOOT[4]) = ON  (logic-1) /* selects NAND Boot */
  SW2.6 (SYSBOOT[5]) = ON  (logic-1) /* selects NAND Boot */
  SW2.7 (SYSBOOT[6]) = OFF (logic-0) /* reserved */
  SW2.8 (SYSBOOT[7]) = OFF (logic-0) /* reserved */

  SW3.1 (SYSBOOT[ 8])= ON  (logic-1) /* selects SYS_CLK1 speed */
  SW3.2 (SYSBOOT[ 9])= OFF (logic-0) /* selects SYS_CLK1 speed */
  SW3.3 (SYSBOOT[10])= ON  (logic-1) /* wait-pin monitoring = enabled */
  SW3.4 (SYSBOOT[11])= OFF (logic-0) /* device type: Addr/Data Muxed */
  SW3.5 (SYSBOOT[12])= ON  (logic-1) /* device type: Addr/Data Muxed */
  SW3.6 (SYSBOOT[13])= ON  (logic-1) /* device bus-width: 1(x16) */
  SW3.7 (SYSBOOT[14])= OFF (logic-0) /* reserved */
  SW3.8 (SYSBOOT[15])= ON  (logic-1) /* reserved */

Following changes are required in board.cfg to enable NAND on J6-EVM: