OMAP2/3: mmc-twl4030: Free up MMC regulators while cleaning up

twl_mmc_cleanup() must free up the regulators that were
allocated by twl_mmc_late_init().
This eliminates the below error when 'omap_hsmmc' module is
repeatedly loaded and unloaded.

"sysfs: cannot create duplicate filename '/devices/platform
 /mmci-omap-hs.0/microamps_requested_vmmc'"

Signed-off-by: Roger Quadros <ext-roger.quadros@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>