Commit 718a350 (ARM: i.MX51: Add PATA support) adds pata support to the
imx51.dtsi file and is using clock 161. The problem is that the right
clock is 172, according to commit 5d530bb (ARM: i.MX5: Add PATA and SRTC
clocks). Using the clock 172 makes things work again (and kills a nasty
system freeze).