Bugfix: `CounterHz` and `Counter` `wait`

[AndreySmirnov81]

CounterHz and Counter do not wait properly after the second and subsequent start.

[burrbull]

It is strange. trigger_update should not cause interrupt.

https://github.com/stm32-rs/stm32f1xx-hal/blob/cafbac16d79da5c56bedb99b8c3f45b2c2463c38/src/timer.rs#L374-L379

Maybe wait doesn't clear flag correctly?

[AndreySmirnov81]

wait clears the flag correctly, however, the timer does not stop and works cyclically, which leads to the fact that the TIMx_SR.UIF flag is constantly set.

[burrbull]

bors r+

[bors[bot]]

Build succeeded:

• ci (stm32f100, stable)
• ci (stm32f101, stable)
• ci (stm32f103, stable)
• ci (stm32f105, stable)
• ci (stm32f107, stable)
• Rustfmt