drm/i915/gt: remove redundant assignment to variable dw

drm/i915/gt: remove redundant assignment to variable dw

Variable dw is being initialized with a value that is never read,
it is assigned a new value later on. The assignment is redundant
and can be removed.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20200222134755.134209-1-colin.king@canonical.com