regulator: fix simple_return.cocci warnings

Simplify a trivial if-return sequence and combine with a
preceding function call.

Generated by: scripts/coccinelle/misc/simple_return.cocci

CC: Mark Brown <broonie@kernel.org>
Signed-off-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Mark Brown <broonie@kernel.org>