regulator: core: Don't spew backtraces on duplicate sysfs

We don't consider a failure to add the sysfs node as a problem,
so use sysfs_create_link_nowarn() so that we don't print a
backtrace when duplicated files exist. Also, downgrade the printk
message to a debug statement so that we're quiet here. This
allows multiple drivers to request a CPU's regulator so that
CPUfreq and AVSish drivers can coexist.

Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Mark Brown <broonie@kernel.org>