staging: gasket: apex: move sysfs setup code to probe function

The gasket framework no longer provides callbacks to the device driver
for sysfs setup and teardown.  Move the sysfs setup code to the device
probe function.  Apex does not implement sysfs cleanup code.

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