ps2kbd: default to scancode_set 2, as with KBD_CMD_RESET

This line has been added in commit ef74679a with
other initializations. However, scancode set 0 doesn't exist (only 1, 2, 3).
This works well as long as operating system is resetting keyboard, or overwriting
the current scancode set with the one it wants.

This fixes IBM 40p firmware, which doesn't bother sending KBD_CMD_RESET or KBD_CMD_SCANCODE.

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Message-Id: <1458714100-28885-1-git-send-email-hpoussin@reactos.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>