drivers: misc: ti-st: Fix a typo ("unknow")

Spell it as "unknown".

Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Link: https://lore.kernel.org/r/20230129161942.1627267-1-j.neuschaefer@gmx.net


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>