Remove target_has_memory macro

Remove target_has_memory macro

This removes the target_has_memory object-like macro, replacing it
with the underlying function.

gdb/ChangeLog
2020-09-28  Tom Tromey  <tom@tromey.com>

	* target.c (target_has_memory): Rename from target_has_memory_1.
	* tui/tui-regs.c (tui_data_window::show_registers): Update.
	* thread.c (scoped_restore_current_thread::restore)
	(scoped_restore_current_thread::scoped_restore_current_thread):
	Update.
	* frame.c (get_current_frame, has_stack_frames): Update.
	* target.h (target_has_memory): Remove macro.
	(target_has_memory): Rename from target_has_memory_1.