panfrost/midgard: Broadcast swizzle

panfrost/midgard: Broadcast swizzle

Fixes regression in shaders using ball/etc by explicitly passing through
the number of channels in the NIR op and broadcasting the last
components of the channel appropriately, as the Midgard ops are all vec4
implicitly but NIR can be vec2/3.

v2: Don't also regress every other swizzle in Equestria.

v3: Don't regress the swizzles at Canterlot High either.

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Acked-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>