power: regulator: max77686: Don't use switch() on bools

power: regulator: max77686: Don't use switch() on bools

With gcc-5.3 we get a warning for using switch() on a bool type.
Rewrite these sections as if/else and update the one section that was
using 1/0 instead of true/false.

Cc: Simon Glass <[email protected]>
Signed-off-by: Tom Rini <[email protected]>
Reviewed-by: Bin Meng <[email protected]>
Acked-by: Przemyslaw Marczak <[email protected]>