[console] Add keymap generator

Inspired by LILO's keytab-lilo.pl, genkeymap.pl uses "loadkeys -b" to
obtain a Linux keyboard map, and generates a file keymap_xx.c in
hci/keymap.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/hci/keymap/keymap_us.c

@@ -0,0 +1,15 @@
+/** @file
+ *
+ * "us" keyboard mapping
+ *
+ * This file is automatically generated; do not edit
+ *
+ */
+
+FILE_LICENCE ( PUBLIC_DOMAIN );
+
+#include <ipxe/keymap.h>
+
+/** "us" keyboard mapping */
+struct key_mapping us_mapping[] __keymap = {
+};