staging: udlfb: remove metrics_misc sysfs attribute

Remove metrics_misc sysfs attribute

Previously returned multiple values, which goes against sysfs guidelines.
Had been used for debugging to figure out which of the multiple
fbdev interfaces an app was using, but log file messages are sufficient.

Signed-off-by: Bernie Thompson <bernie@plugable.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>