I need upgrade a FMC 2500 from version 6.4.0.13 to version 6.6.1.91; the release notes of 6.6 is not clear if need upgrade before to 6.6.0 after to pass to version 6.6.1.91. https://www.cisco.com/c/en/us/td/docs/security/firepower/660/relnotes/firepo...