imx: mx6qpsabreauto: Add MX6QP SABREAUTO CPU3 board support

imx: mx6qpsabreauto: Add MX6QP SABREAUTO CPU3 board support

1. Add DDR script for mx6qpsabreauto board.
2. On CPU3 board, enet RGMII tx clock is from internal PLL. Set the GPR5[9]
   and init the enet pll output to 125Mhz.
3. On CPU3 board, SW1ABC=VDDSOC_IN, SW2=VDDARM_IN.

Build target: mx6qpsabreauto_config

Boot Log:
U-Boot 2015.07-rc2-00071-gfd985ff (Jun 29 2015 - 22:10:55 +0800)

CPU:   Freescale i.MX6QP rev1.0 996 MHz (running at 792 MHz)
CPU:   Automotive temperature grade (-40C to 125C) at 34C
Reset cause: POR
Board: MX6Q-Sabreauto revA
I2C:   ready
DRAM:  2 GiB
PMIC:  PFUZE100 ID=0x10
Flash: 32 MiB
NAND:  0 MiB
MMC:   FSL_SDHC: 0
*** Warning - bad CRC, using default environment

No panel detected: default to HDMI
Display: HDMI (1024x768)
In:    serial
Out:   serial
Err:   serial
Net:   FEC [PRIME]
Hit any key to stop autoboot:  0

Note:
In this patch, we still add a new config mx6qpsabreauto_config,
since SPL is not supported now, and IMX_CONFIG is needed at
build time, so add this config. Future, when SPL is converted,
this config can be removed.

Signed-off-by: Peng Fan <Peng.Fan@freescale.com>
Signed-off-by: Robin Gong <b38343@freescale.com>
Signed-off-by: Ye.Li <B37916@freescale.com>
Reviewed-by: Fabio Estevam <fabio.estevam@freescale.com>