If you would like to hide eazyBI top navigation link then as Jira system administrator go to Jira Administration / Manage add-ons and find eazyBI plugin and expand all modules of the plugin. Then disable eazyBI home link module to hide top navigation bar link:
You can still navigate to
JIRA_BASE_URL/plugins/servlet/eazybi to access eazyBI. In addition you can add text gadget to Jira dashboard with link to eazyBI home page.