regulator: Don't add the function name to pr_fmt

Liam pointed out via IM that since we now use the pure function name for
all regulator logging a lot of the messages such as those logging the
constraints are getting a bit noisy due to the implementation detail
that is the function name:

print_constraints: VDDARM: 1000 <--> 1300 mV at 1300 mV at 0 mA

In discussion it seemed like the best thing was to just drop the pr_fmt
and clarify individual log messages where there is an issue otherwise
we get into silly things like renaming the functions to suit the logging.

This is mostly an issue as we have a moderate amount of non-error logging
in the boot sequence to aid debug if something goes wrong since regulator
misconfiguration can kill the system pretty quickly.

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