ARM: dts: omap3-igep0020: Use MMC pwrseq to init SDIO WiFi

When the WiFi support was added to the IGEP0020 board, the MMC subsystem
did not provide a mechanism to define power sequence providers. So a DT
hack was used to toggle the WiFi chip reset and power down pins by using
fake fixed regulators whose enable GPIO was the GPIOs connected to these
pins.

But now the simple MMC power sequence provider can be used for this and
the workaround removed.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Acked-by: Enric Balletbo Serra <enric.balletbo@collabora.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>