staging: gasket: apex: fix sysfs_show

sysfs_show was incorrectly extracting the sysfs_attribute_type from the
gasket_sysfs_attribute. This prevented dispatch from working properly.

Signed-off-by: Nick Ewalt <nicholasewalt@google.com>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>