You will need a copy of a VC GBA game ready for loadiine.
I suggest TLoZ The Minish Cap because it has the most room in the alldata.bin file.
1. Take a complete copy of the minish cap directory into a new directory named "Super Mario Land 2"
2. inject_gba.py -a "/path/to/Super Mario Land 2/content/alldata.bin" "/path/to/Super Mario Land 2.gba"
3. Copy "Super Mario Land 2.gba.adb" into place as alldata.bin
(This is not automatic because I don't want complaints when someone over-writes their only copy of something.)
cp "/path/to/Super Mario Land 2.gba.adb" "/path/to/Super Mario Land 2/content/alldata.bin"
I tested your rom, it works.