Missing for loop variable 'j' initializor.

Fixed the following error

    [ 15%] Building C object nva/CMakeFiles/nva.dir/nva.c.o
    /home/tomwij/envytools/nva/nva.c: In function ‘nva_init’:
    /home/tomwij/envytools/nva/nva.c:105:9: error: ‘j’ undeclared (first use in this function)
    /home/tomwij/envytools/nva/nva.c:105:9: note: each undeclared identifier is reported only once for each function it appears in
    make[2]: *** [nva/CMakeFiles/nva.dir/nva.c.o] Error 1
    make[1]: *** [nva/CMakeFiles/nva.dir/all] Error 2
    make: *** [all] Error 2

by adding `int j;` before the for loop on [line 105](https://github.com/pathscale/envytools/blob/master/nva/nva.c#L105).