staging: gasket: Fix incongruency in handling of sysfs entries creation

Fix incongruency in handling of sysfs entries creation.
This issue could cause invalid memory accesses, by not properly
detecting the end of the sysfs attributes array.

Fixes: 84c45d5f

 ("staging: gasket: Replace macro __ATTR with __ATTR_NULL")
Signed-off-by: Luis Mendes <luis.p.mendes@gmail.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200403151534.20753-1-luis.p.mendes@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>