s5k3l6xx: remove the autosuspend delay
simplify runtime pm so that it's handled just like any other camera driver does it: remove an autosuspend delay for runtime pm. this delay is an old copy paste relict and an unneeded magic number.
use the non-autosuspend functions only and it's not needed to "mark last busy": https://www.kernel.org/doc/html/latest/power/runtime_pm.html#autosuspend-or-automatically-delayed-suspends