static-nodes: unify return statements

static-nodes: unify return statements

The write_* functions have different return statement handling. Unify
them by removing "else" if the if-block itself returns and also unify
the error handling by checking for the error case, leaving the success
return statement at the end of the function.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Link: https://github.com/kmod-project/kmod/pull/285
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>