Backport 'ARM: imx: soc: Select default TEXT_BASE for MX7' to v2020.04+fslc

[maximdeclercq]

Problem
Branch v2020.04+fslc does not boot on i.MX7D systems.
The issue is explained in a1f6d04.

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.

Proposed solution
Backporting a1f6d04 to the v2020.04+fslc branch should resolve this issue.

[maximdeclercq]

Branch 2020.04+fslc is also the default in Yocto dunfell, which should be supported until Apr. 2024.

[otavio]

I'm not against this but you need to prepare the pr.