Unable to boot Zephyr on FVP_BaseR_AEMv8R

[cfriedt]

Describe the bug

In the Armv8R AArch64 profile, the Armv8R AArch64 is always in secure mode. But the FVP_BaseR_AEMv8R before version 11.16.16 doesn't strictly follow this rule. It still has some non-secure registers(e.g. CNTHP_CTL_EL2).

The issue is:
Since version 11.16.16, the FVP_BaseR_AEMv8R has fixed this issue. The CNTHP_XXX_EL2 registers have been changed to CNTHPS_XXX_EL2. So the FVP_BaseR_AEMv8R (version >= 11.16.16) cannot boot Zephyr.

This PR will fix it:
Also means, after the fix, the minimum required version of FVP will be 11.16.16. Since there is almost no one uses the version less than 11.16.16 and also no way to download the older versions, I think I will not spend time doing the logic of the fvp version checking. It's enough to add an announcement of the minimum required FVP version in the board doc