drivers: pwm: pwm_stm32: Add error log for 16-bit timer buffer overflow

If the value in the period_cycles variable exceeds UINT16_MAX, a 16-bit
timer will return an error code 134. An error message was added to
indicate that the value does not fit into the 16-bit timer register.
An error message advising developers to reduce the value to 16-bit
simplifies the process, allowing them to understand immediately that
reducing the value will resolve the issue.

Signed-off-by: Marek Sroka <m.sroka14@gmail.com>