mfd: twl-core: Don't specify regulator consumers by struct device

This has been deprecated for considerable time now and support has been
removed from the regulator API. dev_name should be used instead.

Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>