drm/fourcc: Fix conflicting Y41x definitions

There has unfortunately been a conflict with the following 3 commits:

commit e9961ab9
Author: Ayan Kumar Halder <ayan.halder@arm.com>
Date:   Fri Nov 9 17:21:12 2018 +0000
    drm: Added a new format DRM_FORMAT_XVYU2101010

commit 7ba0fee2
Author: Brian Starkey <brian.starkey@arm.com>
Date:   Fri Oct 5 10:27:00 2018 +0100

    drm/fourcc: Add AFBC yuv fourccs for Mali

and

commit 50bf5d7d
Author: Swati Sharma <swati2.sharma@intel.com>
Date:   Mon Mar 4 17:26:33 2019 +0530

    drm: Add Y2xx and Y4xx (xx:10/12/16) format definitions and fourcc

Unfortunately gcc didn't warn about the redefinitions, because the
double defines were the set to same value, and gcc apparently no longer
warns about that.

Fix this by using new XYVU for i915, without alpha, and making the
Y41x definitions match msdn, with alpha.

Fortunately we caught it early, and the conflict hasn't even landed in
drm-next yet.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Brian Starkey <Brian.Starkey@arm.com>
Cc: Swati Sharma <swati2.sharma@intel.com>
Cc: Ayan Kumar Halder <ayan.halder@arm.com>
Cc: malidp@foss.arm.com
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Maxime Ripard <maxime.ripard@bootlin.com>
Cc: Sean Paul <sean@poorly.run>
Cc: Dave Airlie <airlied@linux.ie>
Cc: Liviu Dudau <Liviu.Dudau@arm.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190319121702.6814-1-maarten.lankhorst@linux.intel.com


Acked-by: Jani Nikula <jani.nikula@intel.com> #irc
Acked-by: Sean Paul <sean@poorly.run>
Reviewed-by: Ayan Kumar halder <ayan.halder@arm.com>