drm/i915: remove trailing semicolon in macro definition

The macro use will already have a semicolon.

Signed-off-by: Tom Rix <trix@redhat.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/20201127162828.2660230-1-trix@redhat.com