regulator: Make constraint debug processing conditional on DEBUG

If debugging is disabled, print_constraints() does not print the actual
constraints, but still performs some processing and string formatting,
only to throw away the result later.

Fix this by moving all constraint debug processing to a separate
function, and replacing it by a dummy when debugging is disabled.
This reduces kernel size by almost 800 bytes (on arm/arm64).

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20201005131546.22448-1-geert+renesas@glider.be


Signed-off-by: Mark Brown <broonie@kernel.org>