platform/x86: thinkpad_acpi: Move hkey > scancode mapping to tpacpi_input_send_key()

Move the mapping of hkey events to scancodes to tpacpi_input_send_key(),
this results in a nice cleanup and prepares things for adding sparse-keymap
support.

Tested-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/20240424122834.19801-14-hdegoede@redhat.com