ARM: pxa: propagate errors from regulator_enable() to pxamci

The em_x270_mci_setpower() and em_x270_usb_hub_init() functions
call regulator_enable(), which may return an error that must
be checked.

This changes the em_x270_usb_hub_init() function to bail out
if it fails, and changes the pxamci_platform_data->setpower
callback so that the a failed em_x270_mci_setpower call
can be propagated by the pxamci driver into the mmc core.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Mike Rapoport <mike@compulab.co.il>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Haojian Zhuang <haojian.zhuang@gmail.com>
Acked-by: Chris Ball <cjb@laptop.org>
[olof: fixed order of regulator_enable() and test in em_x270_usb_hub_init]
Signed-off-by: Olof Johansson <olof@lixom.net>