ARM: 6163/1: at91sam9g20ek: add fixed-value regulator for wm8731

If CONFIG_REGULATOR is enabled, wm8731 fails on AT91SAM9G20EK board,
since codec driver requires several voltage supplies and none are
provided currently. As requires voltages are hardwired to 3V3, use fixed
voltage regulator for this chip.

Signed-off-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Acked-by: Andrew Victor <linux@maxim.org.za>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>