uEnv.txt

...
optargs=capemgr.disable_partno=BB-BONELT-HDMI,BB-BONELT-HDMIN
...

root@arm:~# export SLOTS=/sys/devices/bone_capemgr.*/slots
root@arm:~# cat $SLOTS
 0: 54:PF---
 1: 55:PF---
 2: 56:PF---
 3: 57:PF---
 4: ff:P-O-L Bone-LT-eMMC-2G,00A0,Texas Instrument,BB-BONE-EMMC-2G
 5: ff:P-O-- Bone-Black-HDMI,00A0,Texas Instrument,BB-BONELT-HDMI
 6: ff:P-O-- Bone-Black-HDMIN,00A0,Texas Instrument,BB-BONELT-HDMIN