power: supply: core: reduce loglevel for probe defer info

Avoid logging probe defer information for default loglevel
configurations. This is only required for debugging probe
defer issues, which requires enabling debug messages for
other subsystems.

This dev_info() message predates having deferred devices
information available in /sys/kernel/debug/devices_deferred,
which is generally more useful.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>