[X86] Remove [ER]SP from all CSR lists

Authored by rnk on Jan 5 2021, 1:45 PM.


[X86] Remove [ER]SP from all CSR lists

The CSR lists control which registers are spilled and reloaded in the
prologue and epilogue. The stack pointer is managed explicitly, and
should never be pushed or popped. Remove it from these lists. This
affected regcall and preserves all / most.

Differential Revision: https://reviews.llvm.org/D94118