platform/x86: thinkpad_acpi: Restore missing hotkey_tablet_mode and hotkey_radio_sw sysfs-attr

Commit c99ca78d ("platform/x86: thinkpad_acpi: Switch to common use
of attributes") removed the conditional adding of the
hotkey_tablet_mode and hotkey_radio_sw sysfs-attributes, replacing this
with a hotkey_attr_is_visible() callback which hides them when the
feature is not present.

But this commit forgot to add these 2 attributes to the default
hotkey_attributes[] set, so they would now never get added at all.

Add the 2 attributes to the default hotkey_attributes[] set so that
they are available on systems with these features once more.

Fixes: c99ca78d ("platform/x86: thinkpad_acpi: Switch to common use of attributes")
Cc: Len Baker <len.baker@gmx.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20211123210424.266607-2-hdegoede@redhat.com