ARM: imx: soc: Select default TEXT_BASE for MX7

Select default U-Boot and SPL text base for the MX7 SoC. The U-Boot
text base is picked as the one used by various MX7 boards. The SPL
text base however is different.

The SPL text base is set to 0x912000 instead of the usual 0x911000,
that is because the 0x911000 value cannot work. Using 0x911000 as a
SPL text base will result in the DCD header being placed below the
0x911000 address, which is a reserved SRAM area which must not be
used. This will actually trigger eMMC boot failure on MX7D at least.
Hence the increment.

Update all boards affected by this SPL problem to the new SPL_TEXT_BASE.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@gmail.com>
Cc: NXP i.MX U-Boot Team <uboot-imx@nxp.com>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>