afs.c: Remove enum afs_table_num.

afs.c: Remove enum afs_table_num.

The definition of afs_tables[] does not need this enumeration to
initialize the array and everybody else just needs the number of
elements which can as well be obtained with ARRAY_SIZE.

Since enum values are of type int but ARRAY_SIZE expands to a size_t
value we need an adjustment for a format string in open_afs_tables().