drivers: counter: smartbond: Add support for PM

This commit should add all the functionality needed for the counter
driver to work when PM is enabled. The sleep state is bound to the
counter start/stop functionality. TIMER3/4 block instances are
powered by PD_SYS and so sleep should be constrained when they are
up and running. On the other hand TIMER1/2 block instances are
powered by PD_TMR which is always on (used to generate the os tick).

Signed-off-by: Ioannis Karachalios <ioannis.karachalios.px@renesas.com>