[POWERPC] spufs: fix use time accounting on SPE-overcommit

The spu_runcntl_RW register is restored within spu_restore function.
So, at the end of spu_bind_context, the SPU context is not just loaded,
but running.

This change corrects the state switch to account the time as USER.

Signed-off-by: Andre Detsch <adetsch@br.ibm.com>
Signed-off-by: Jeremy Kerr <jk@ozlabs.org>