ir-rx51: use hrtimer instead of dmtimer

Drop dmtimer usage for pulse timer in favor of hrtimer. That allows
removing PWM dmitimer platform data usage.

Signed-off-by: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Acked-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>