x86-64: Save APX registers in ld.so trampoline

Add APX registers to STATE_SAVE_MASK so that APX registers are saved in
ld.so trampoline.  This fixes BZ #31371.

Also update STATE_SAVE_OFFSET and STATE_SAVE_MASK for i386 which will
be used by i386 _dl_tlsdesc_dynamic.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>