libfuse: rename fuse to libfuse

We rename the package/fuse directory to package/libfuse to be
consistent with the package name. This is needed for a future commit
that will simplify the AUTOTARGETS macro by making assumptions on the
directory name.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>