iio: dac: mcp4725: set iio name property in sysfs

commit 97a249e98a72d6b79fb7350a8dd56b147e9d5bdb upstream.

Without this change, the name entity for mcp4725 is missing in
/sys/bus/iio/devices/iio\:device*/name

With this change, name is reported correctly

Signed-off-by: Yong Li <sdliyong@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>