fuzz/x86_emulate: Rename the file containing the wrapper code

fuzz/x86_emulate: Rename the file containing the wrapper code

When generating coverage output, by default gcov generates output
filenames based only on the coverage file and the "leaf" source file,
not the full path.  As a result, it uses the same name for
x86_emulate.c and x86_emulate/x86_emulate.c, generally overwriting the
second (which we actually are about) with the first (which is just a
wrapper).

Rename the user-space wrapper helpers to x86-emulate.[ch], so
that it generates separate files.

There is actually an option to gcov, `--preserve-paths`, which will
cause the full path name to be included in the filename, properly
distinguishing between the two.  However, given that the user-space
wrapper doesn't actually do any emulation (and the poor state of gcov
documentation making it difficult to find the option in the first
place), it seems to make more sense to rename the file anyway.

Signed-off-by: George Dunlap <george.dunlap@citrix.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>