Remove tui_data_window::display_all_data

Remove tui_data_window::display_all_data

tui_data_window::rerender clears the data item windows, and then calls
display_all_data.  However, that method only does anything if the
contents are not empty.  So, display_all_data can be renamed and the
wrapper removed.

gdb/ChangeLog
2019-08-30  Tom Tromey  <tom@tromey.com>

	* tui/tui-regs.h (struct tui_data_window) <display_all_data>:
	Don't declare.
	* tui/tui-regs.c (tui_data_window::show_registers): Call
	rerender.
	(tui_data_window::rerender): Rename from display_all_data.
	(tui_data_window::rerender): Remove old implementation.