Man of Honour
M2_1, SATA3_0, SATA3_1 and SATA_EXP_0 share lanes. If either one of them is in use, the others will be disabled, so it should leave you with 4 x sata3 ports working.
http://www.asrock.com/mb/Intel/Z170 Extreme4/?cat=Specifications
http://www.asrock.com/mb/Intel/Z170 Extreme4/?cat=Specifications