[S] Change in libgfxinit[main]: gfxtest: Introduce `From_RGBA` constructor for `Pixel_Type`

[Angel Pons (Code Review)]

Attention is currently required from: Nico Huber.

Angel Pons has posted comments on this change. ( https://review.coreboot.org/c/libgfxinit/+/81854?usp=email )

Change subject: gfxtest: Introduce `From_RGBA` constructor for `Pixel_Type`
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Patch Set 1:

(3 comments)

Commit Message:

https://review.coreboot.org/c/libgfxinit/+/81854/comment/ffa00fee_2d9624a0 :
PS1, Line 7: gfxtest: Fix out-of-order components, permanently
> Technically, there is nothing to fix, how about: […]

Done

File gfxtest/hw-gfx-gma-gfx_test.adb:

https://review.coreboot.org/c/libgfxinit/+/81854/comment/bb3b775f_d48ac364 :
PS1, Line 60:    for Pixel_Type use record
            :       Blue  at 0 range 0 .. 7;
            :       Green at 1 range 0 .. 7;
            :       Red   at 2 range 0 .. 7;
            :       Alpha at 3 range 0 .. 7;
            :    end record;
> Could replace this with a `with Packed` for the record then.

Used a `with Pack`, if this record's size ever happens to not be 32 bits, at least the `Unchecked_Conversion` to `Word32` will cause a warning.

https://review.coreboot.org/c/libgfxinit/+/81854/comment/86d9a4c4_adecfcee :
PS1, Line 67: RGB
> or `From_RGBA`?

Done