ARM: pxa: fix dm9000 platform data regression

Since dm9000 driver added support for a vcc regulator, platform data
based platforms have their ethernet broken, as the regulator claiming
returns -EPROBE_DEFER and prevents dm9000 loading.

This patch fixes this for all pxa boards using dm9000, by using the
specific regulator_has_full_constraints() function.

This was discovered and tested on the cm-x300 board.

Fixes: 7994fe55 ("dm9000: Add regulator and reset support to dm9000")
Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Acked-by: Igor Grinberg <grinberg@compulab.co.il>