No, there is not a specific form you need to fill out in order to indicate that you switched from being an independent contractor to an employee for the same company.
The IRS will not flag your return as possible misclassification if you include your Wages reported on your W2 on Line 1 of your Form 1040 and your 1099-MISC income (and any related expenses) on your Schedule C.
It is actually quite common for an independent contractor to be hired on as an employee.
