* dwarf2-frame-tailcall.c: Include dwarf2-frame.h.
(dwarf2_tailcall_prev_register_first): Use dwarf2_frame_cfa.
(dwarf2_tailcall_sniffer_first): Remove variable pc_regnum. Replace
gdbarch_pc_regnum and frame_unwind_register_unsigned by
gdbarch_unwind_pc.