This is how I edited the second menu item in bootmenu.conf:

[...]

MENU_2_NAME="Internal MMC card, partition 3, ext3"
MENU_2_ID="immc3"
MENU_2_DEVICE="${INT_CARD}p3"
MENU_2_MODULES="mbcache jbd ext3"
MENU_2_FSTYPE="ext3"
MENU_2_FSOPTIONS="noatime,ro"
MENU_2_LINUXRC="linuxrc"
[...]