Re: [tip: x86/asm] x86/asm: Make ASM_CALL_CONSTRAINT conditional on frame pointers

[Andrew Cooper]

> One more thing: if we remove ASM_CALL_CONSTRAINTS, we will not be able to use the redzone in future FRED only kernel builds.

That's easy enough to fix with "|| CONFIG_FRED_EXCLUSIVE" in some
theoretical future when it's a feasible config to use.

~Andrew