power-supply: Drop useless 'if (ret.intval)' statements

There is no need to check the value of ret.intval before returning it, as we
will be returning zero explicitly when ret.intval is zero.

So essentially we will end up returning value of ret.intval as it is. Drop the
unnecessary 'if' statements.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Sebastian Reichel <sre@kernel.org>