[settings] Add support for navigation keys in "config" user interface

Add support for page up, page down, home and end keys, matching the
navigation logic used in the menu user interface.

Originally-implemented-by: Marin Hannache <git@mareo.fr>
Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/hci/tui/settings_ui.c

 			key = getkey ( 0 );
 			move = 0;
 			switch ( key ) {
+			case KEY_UP:
+				move = -1;
+				break;
 			case KEY_DOWN:
-				if ( widget.current < ( widget.num_rows - 1 ) )
-					move = +1;
+				move = +1;
 				break;
-			case KEY_UP:
-				if ( widget.current > 0 )
-					move = -1;
+			case KEY_PPAGE:
+				move = ( widget.first_visible -
+					 widget.current - 1 );
+				break;
+			case KEY_NPAGE:
+				move = ( widget.first_visible - widget.current
+					 + SETTINGS_LIST_ROWS );
+				break;
+			case KEY_HOME:
+				move = -widget.num_rows;
+				break;
+			case KEY_END:
+				move = +widget.num_rows;
 				break;
 			case CTRL_D:
 				if ( ! widget.row.setting )
 			}
 			if ( move ) {
 				next = ( widget.current + move );
-				draw_setting_row ( &widget );
-				redraw = 1;
-				reveal_setting_row ( &widget, next );
-				select_setting_row ( &widget, next );
+				if ( ( int ) next < 0 )
+					next = 0;
+				if ( next >= widget.num_rows )
+					next = ( widget.num_rows - 1 );
+				if ( next != widget.current ) {
+					draw_setting_row ( &widget );
+					redraw = 1;
+					reveal_setting_row ( &widget, next );
+					select_setting_row ( &widget, next );
+				}
 			}
 		}
 	}