hx4700: regulator: declare full constraints

commit a52d209336f8fc7483a8c7f4a8a7d2a8e1692a6c upstream.

Since the removal of CONFIG_REGULATOR_DUMMY option, the touchscreen stopped
working. This patch enables the "replacement" for REGULATOR_DUMMY and
allows the touchscreen to work even though there is no regulator for "vcc".

Signed-off-by: Martin Vajnar <martin.vajnar@gmail.com>
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>