drm/i915/guc: remove unneeded goto from selftest

commit e346a991 ("drm/i915/guc: drop negative doorbell alloc
selftest") removed the negative case from the selftest and left no
code between the goto from the positive case of the test and the label
itself, so we can get rid of it.

Reported-by: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20181022230427.5616-5-daniele.ceraolospurio@intel.com