Revert "mmc: host: omap_hsmmc: use regulator_is_enabled to find pbias status"

This reverts commit c55d7a05.

Without reverting this commit we get "unbalanced disables for pbias_mmc_omap4"
errors on omap4430. It seems that 4430 and 4460 behave in a different way for
the PBIAS regulator registers and until that has been debugged further we
cannot rely on the regulator status registers in hardare on 4430.

Fixes: 7d607f91 ("mmc: host: omap_hsmmc: use
devm_regulator_get_optional() for vmmc")
Cc: Felipe Balbi <balbi@ti.com>
Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Nishanth Menon <nm@ti.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Tested-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>