regulator: empty the old suspend functions

Regualtor suspend/resume functions should only be called by PM suspend
core via registering dev_pm_ops, and regulator devices should implement
the callback functions.  Thus, any regulator consumer shouldn't call
the regulator suspend/resume functions directly.

In order to avoid compile errors, two empty functions with the same name
still be left for the time being.

Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>