drm/i915/uc: Remove redundant ucode offset definition

According to Firmware layout definition, uCode is located right
after CSS header, so ucode offset is always same as header size.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20190726184212.1836-2-michal.wajdeczko@intel.com