EDAC: Make edac_debugfs_create_x*() return void

The return values of edac_debugfs_create_x16() and
edac_debugfs_create_x8() are never checked (as they don't need to be),
so no need to have them return anything, just make the functions return
void instead.

This is done with the goal of being able to change the debugfs_create_x*
functions to also not return a value.

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: James Morse <james.morse@arm.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
Link: https://lkml.kernel.org/r/20190611175433.GA5108@kroah.com