Allow open drain timer pin

[andrej-mk]

I2C SDA and SCL pins use similar approach - they accept Output<OpenDrain> and then set alternate function mode.

• remove generic MODE parameter from macro invocations
• generate TimerPin trait impl for Analog and Output<OpenDrain> modes

[andresv]

Could you fix formatting with cargo fmt.

[andrej-mk]

Done. I've run cargo fmt.

[dotcypress]

Thank you @andrej-mk!