PMIC PF1550 is supported by NXP Linux BSP. Use section 2.5.2 (PMIC PF Regulator)
of i.MX Linux Reference Manual (Rev. L5.4.24_2.1.0) for more details.
In L5.4.24_2.1.0 I see the pf1550-regulator-rpmsg driver but not the pf1550 client driver. I just checked and the client driver was available in the 4.19.35_1.1.0 release (pf1550.c) but has been removed in latest BSP. I also noticed the pf1550 charger driver was removed in the latest release, pf1550-charger.c in /drivers/power/supply.
Do I have to use the rpmsg drive now, even in a iMX6ULZ application? What about the battery charger driver as that has now been removed?
Yes, It has been removed from L5.4.24_2.1.0 release. However, if customers are using pf1550 with i.MX6ULZ then they can still port/integrate those drivers in their BSP. The BSP team has been requested about reasons behind the removal of the driver; I will inform You in case of an update.