ExifInterface: Add missing ifd format name "IFD"

There has been IFD_FORMAT_IFD = 13 but IFD_FORMAT_NAMES[13]
was not defined, which could throw ArrayIndexOutOfBoundsException.

By providing proper name, we can prevent the exception.

Test: atest exifinterfacetest
Change-Id: Ib11b83a55d54ad2fc6377bb5cc55f6c2fdbe231c