EDAC, thunderx: Fix memory leak in thunderx_l2c_threaded_isr()

Fix memory leak in L2c threaded interrupt handler.

 [ bp: Rewrite commit message. ]

Fixes: 41003396 ("EDAC, thunderx: Add Cavium ThunderX EDAC driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
CC: David Daney <david.daney@cavium.com>
CC: Jan Glauber <jglauber@cavium.com>
CC: Mauro Carvalho Chehab <mchehab@kernel.org>
CC: Sergey Temerkhanov <s.temerkhanov@gmail.com>
CC: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/20181013102843.GG16086@mwanda