staging: lustre: libcfs: use static const char const * for a suffixes array

Change the static const array libcfs_debug_subsystems
to use static const char const * as pointed out by
checkpatch.

Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>