armv8: Support loading 32-bit OS in AArch32 execution state

This series is to support loading a 32-bit OS, the execution state will change from AArch64 to AArch32 when jumping to kernel. The architecture information will be got through checking FIT image, then U-Boot will load 32-bit OS or 64-bit OS automatically.

Spin-table method is used for secondary cores to load 32-bit OS.
The architecture information will be got through checking FIT image and saved in the os_arch element of spin-table, then the secondary cores will check os_arch and jump to 32-bit OS or 64-bit OS automatically.

PSCI method can also be used for secondary cores to load 32-bit OS.
As PSCI and secure monitor firmware framework are enabled, loading 32-bit OS is supported in such case. The default target exception level returned to U-Boot is EL2, so the corresponding work to switch to AArch32 EL2 and jump to 32-bit OS are done in U-Boot and secure firmware together.

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Changes in v8:
- Fix the issue when U-Boot is running in EL2 or EL1.
- Support loading 32-bit OS with PSCI enabled.

Changes in v7:
- Move the call for armv8_switch_to_el2_m into the first patch.

Changes in v6:
- Modified armv8_switch_to_el1(). It will always jump to ep when switching to AArch64 or AArch32 modes.
- Make other platforms compatible with the new armv8_switch_to_el2() and armv8_switch_to_el1().
- Make secondary_switch_to_el1() always jump to ep when switching to AArch64 or AArch32 modes.

Changes in v5:
- Modified armv8_switch_to_el2(). It will always jump to ep when switching to AArch64 or AArch32 modes.
- Make secondary_switch_to_el2() always jump to ep when switching to AArch64 or AArch32 modes.

Changes in v4:
- Correct config ARM64_SUPPORT_AARCH32.
- Omit arch and ftaddr arguments.
- Rename "xreg5" to "tmp".
- Use xxx_RES1 to combine all RES1 fields in xxx register.
- Use an immediate cmp directly.
- Use #ifdef for CONFIG_ARM64_SUPPORT_AARCH32.

Changes in v3:
- Comments the functions and the arguments.
- Rename the real parameters.
- Use the macros instead of the magic values.
- Remove the redundant codes.
- Clean up all of the mess in boot_jump_linux().
- Add CONFIG_ARM64_SUPPORT_AARCH32 to detect for some ARM64 system doesn't support AArch32 state.
- Adjust the arguments for armv8_switch_to_el2_m and armv8_switch_to_el1_m.

Changes in v2:
- armv8_switch_to_el2_aarch32() is removed. armv8_switch_to_el2_m is used to switch to AArch64 EL2 or AArch32 Hyp.
- armv8_switch_to_el1_aarch32() is removed. armv8_switch_to_el1_m is used to switch to AArch64 EL1 or AArch32 SVC.
- Support to call armv8_switch_to_el2_m and armv8_switch_to_el1_m.

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Alison Wang (3):
armv8: Support loading 32-bit OS in AArch32 execution state

armv8: fsl-layerscape: SMP support for loading 32-bit OS
armv8: fsl-layerscape: Support loading 32-bit OS with PSCI enabled