pwm: stm32: Fix a typo

Fix a typo in comments.

Reported-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Andrew Kreimer <algonell@gmail.com>
Link: https://lore.kernel.org/r/20240912124944.43284-1-algonell@gmail.com


Signed-off-by: Uwe Kleine-König <ukleinek@kernel.org>