drivers/regulator: include <module.h> for modular max77802 code

This file is built off of a tristate Kconfig option and also contains
modular function calls so it should explicitly include module.h to
avoid compile breakage during header shuffles done in the future.

Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>