pckbd: return 'keyboard enabled' on read input port command

pckbd: return 'keyboard enabled' on read input port command

Bit 7 of Input Port is the keyboard inhibit switch.
0 means keyboard inhibited, while 1 means keyboard enabled.

Incidentaly, this also fixes an error encountered while booting
an Award BIOS: "Keyboard is locked out - Unlock the key".

Signed-off-by: Hervé Poussineau <hpoussin@reactos.org>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>