nconf: add u, d command keys in scroll windows

They function just like they do in less(1).
Also correct some discrepancy between the help text and the code wrt
function keys.

Signed-off-by: Benjamin Poirier <bpoirier@suse.de>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/scripts/kconfig/nconf.gui.c b/scripts/kconfig/nconf.gui.c
index 3b18dd8..379003c 100644
--- a/scripts/kconfig/nconf.gui.c
+++ b/scripts/kconfig/nconf.gui.c
@@ -604,9 +604,11 @@
 		switch (res) {
 		case KEY_NPAGE:
 		case ' ':
+		case 'd':
 			start_y += text_lines-2;
 			break;
 		case KEY_PPAGE:
+		case 'u':
 			start_y -= text_lines+2;
 			break;
 		case KEY_HOME:
@@ -632,10 +634,10 @@
 			start_x++;
 			break;
 		}
-		if (res == 10 || res == 27 || res == 'q'
-		    || res == KEY_F(F_BACK) || res == KEY_F(F_EXIT)) {
+		if (res == 10 || res == 27 || res == 'q' ||
+			res == KEY_F(F_HELP) || res == KEY_F(F_BACK) ||
+			res == KEY_F(F_EXIT))
 			break;
-		}
 		if (start_y < 0)
 			start_y = 0;
 		if (start_y >= total_lines-text_lines)