power: supply: Add error checking of psy desc during registration

Currently there's no error checking of this parameter in the
registration function and it's blindly added to psy class and
subsequently used as is. For example if this is NULL the call
to psy_register_thermal() will try to dereference the pointer
thus causing a kernel dump.

This commit updates the registration code to add some basic
checks on the desc pointer validity, name, and presence of
properties.

Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Reviewed-by: Sebastian Reichel <sebastian.reichel@collabora.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>