OMAP2: Devkit8000: Fix mmc regulator failure

This patch fixes the following error:

>regulator: VMMC1: 1850 <--> 3150 mV at 3000 mV normal standby
>twl_reg twl_reg.6: can't register VMMC1, -22
>twl_reg: probe of twl_reg.6 failed with error -22

Signed-off-by: Thomas Weber <weber@corscience.de>
Signed-off-by: Tony Lindgren <tony@atomide.com>