If you look at schematic of HDMI board (page 2), you can see that pins 44 and 46 of expansion connector are named as SD0 and WS. The same pins are connected to CSIO_DAT16 and CSIO_DAT17 at the i.MX53 Quick Start Board - R.
I don't have MCIMXHDMICARD at home, but from schematic I am expected, that you have to populate R150 and R151 on the MCIMXHDMICARD.
I hope that my reply is answer to your question ;-)
Download and unzip this package: Freescale: i.MX53 QuickStart Board Design File for HDMI Board - element14
There is PDF document with schematics. Pins 26, 28, 32, 34, 56 and 58 of expansion connector on the HDMI card side aren't connect. These appropriate pins means signals (in the same order) CSIO_DAT12, CSIO_DAT13, CSIO_DAT14, CSIO_DAT15, CSIO_DAT18 and CSIO_DAT19.
Thus, it's impossible to use those signals at HDMI board :-(