Re: [PATCH] drm/pl111: Advertise no pixel blending

[Roshan Kumar]

No physical PL111 hardware here; I tested under QEMU vexpress with
panic_on_warn, which is also how the syzkaller instance hits this.

On current master (7.3-rc2) the unpatched driver registers and
immediately warns: "[PLANE:35:plane-0] pixel format with alpha exposed
but blend mode not setup", which kills the boot with panic_on_warn.
With v3 below, the same boot registers pl111 with no warnings at all.
One note: 860e748bddcc is not in v7.2, so the splat only shows up on
master/7.3 and later.

v3 also removes the alpha formats from the board-specific tables in
pl111_versatile.c that the sashiko review caught v2 missing.