regulator: core: Allow multiple requests of a single supply mapping

Sometimes it may be useful to allow a device to request a supply multiple
times, for example in order to allow framework management of some uses of
the supply with some additional driver specific management or in order to
allow multiple children of an MFD to work with the supply. Currently this
is not possible due to the creation of

Solve this by removing the requested_uA entry (we have no current users
of this feature anyway) and ignoring errors creating the symlink to the
consumer. We should do something nicer than this as this causes sysfs to
spew enormous warnings but it allows users to run for now.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>