pm: esp32: Fix support to pad hold function

Both GPIO and RTC IO pad types support pad hold function.
Current implementation is only covering digital GPIOs. If the user
selects an RTC IO pin with `sleep-hold-en`, an `abort()` inside the
HAL can happen, depending on the SoC. Extend the implementation to
handle RTC IO pads through the correct hold path and add proper
validation with a warning for pads that support neither hold type.

Signed-off-by: Raffael Rostagno <raffael.rostagno@espressif.com>