regulator: build fix for powerpc - renamed show_state

This patch fixes the follwing build failure on powerpc:-

> Today's linux-next build (powerpc allyesconfig) failed like this:
>
> drivers/regulator/userspace-consumer.c:43: error: conflicting types
> for 'show_state'
> include/linux/sched.h:273: note: previous definition of 'show_state'
> was here
>
> Caused by commit 5defa2bce704ca4151cfe24e4297aa7797cafd22 ("regulator:
> add userspace-consumer driver") which I have reverted for today.

Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>