param: fix return value handling in param_set_*

In STANDARD_PARAM_DEF, param_set_* handles the case in which strtolfn
returns -EINVAL but it may return -ERANGE. If it returns -ERANGE,
param_set_* may set uninitialized value to the paramerter. We should handle
both cases.

The one of the cases in which strtolfn() returns -ERANGE is following:

 *Type of module parameter is long
 *Set the parameter more than LONG_MAX

Signed-off-by: Satoru Moriya <satoru.moriya@hds.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>