scripts/gdb: fix lx-lsmod refcnt

Commit 2f35c41f

 ("module: Replace module_ref with atomic_t refcnt")
changes the way refcnt is handled but did not update the gdb script to
use the new variable.

Since refcnt is not per-cpu anymore, we can directly read its value.

Signed-off-by: Adrien Schildknecht <adrien+dev@schischi.me>
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Pantelis Koukousoulas <pktoss@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>