Remove references to EISA support from the vx driver, along with EISA

Remove references to EISA support from the vx driver, along with EISA
support. Fix a comment block that's shared with both vx and ep. Remove
obsolete refernce to statically compiling a kernel with a fixed number
of vx devices. Have not removed EISA from the title of the document
the register definitions were originally derived from (though no doubt
more recent docments were also consulted).