There's a couple of issues here.
First, one doesn't execute a Makefile, instead you run "make" and it will look for the file named "Makefile", capitalization I believe applies. If you use a different name or the Makefile is in a different path than the current working directory, then you can issue "make -f <make-file-name>" however I'm not sure doing that from a different path is a good choice. What I've seen is a Makefile or a series of them will change directory to where the Makefile is located and then run the "make" command.
Neither here nor there, you created a Makefile on your own and the second issue is that you likely are not properly set up to compile this correctly in any case. It is a driver, and thus a kernel module. And there are certain things you need to do to be able to compile kernel modules. You need to obtain the module sources and the kernel headers. I don't know the full set of steps for an existing distribution, but a good search would be "Beagleboard xM how to build kernel modules" and that may give you some better guidance.
Also I think the xM is old, not sure. I'm am sure that the Beagleboard Black is the newest and most recently maintained one. I do know that the
Beagleboard google groups are maintained pretty well by Robert C Nelson, he is pretty responsive if you ask questions.
