x86: also permit YMM/ZMM use in CFI directives

x86: also permit YMM/ZMM use in CFI directives

Next to code using %ymm<N> or %zmm<N> it is more natural to have .cfi_*
directives also reference those, not the corresponding %xmm<N>. Accept
their names as kind of aliases, i.e. resolving to the same numbers.

While extending the respective 64-bit testcase, also add %bnd<N> there
(should have happened right with 633789901c83 ["x86-64: Dwarf2 register
numbers for %bnd<N>"], sorry), requiring binutils/dwarf.c to be adjusted
accordingly as well.