New field with limited cardinality cannot be created.

Problem/Motivation

Trying to create a new field while having entities of a bundle in the database ends up in a failure.

Steps to reproduce

* Create an entity type (or use rdf_entity).
* Create a bundle in that type.
* Create an entity of that bundle.
* Try to add a text field or any field type in that bundle but with limited cardinality.

Expected result:
The form is submitted successfully.
Actual result:
An error saying that there is 1 entity with more than the cardinality selected is raised.

Proposed resolution

Remove the cardinality check when creating the field.