toshiba_acpi: Add 0x prefix to available_kbd_modes_show function

This patch adds the 0x prefix to the values printed by such function, the
values are already being printed in hex, but without the prefix, causing
confusion, even though the file under Documentation/ABI clearly states
that hey are hex values.

Simply add the 0x prefix to avoid such confusion.

Signed-off-by: Azael Avalos <coproscefalo@gmail.com>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>