ARM: 7721/1: mmc: mmci: Fixup regulator handling for vqmmc

We can not rely on regulator_is_enabled to decide whether to
enable|disable the regulator. It would mean that the reference
counter for it is not balanced properly.

Instead keep track of our internal state by using a new flag in
the host struct, so we can take correct decisions.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>