PCI/VGA: Don't assume the only VGA device on a system is `boot_vga`

PCI/VGA: Don't assume the only VGA device on a system is `boot_vga`

Some systems ship with multiple display class devices but not all
of them are VGA devices. If the "only" VGA device on the system is not
used for displaying the image on the screen marking it as `boot_vga`
because nothing was found is totally wrong.

This behavior actually leads to mistakes of the wrong device being
advertised to userspace and then userspace can make incorrect decisions.

As there is an accurate `boot_display` sysfs file stop lying about
`boot_vga` by assuming if nothing is found it's the right device.

Reported-by: Aaron Erhardt <aer@tuxedocomputers.com>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220712
Tested-by: Aaron Erhardt <aer@tuxedocomputers.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Fixes: ad90860bd10ee ("fbcon: Use screen info to find primary device")
Tested-by: Luke D. Jones <luke@ljones.dev>
Signed-off-by: Mario Limonciello (AMD) <superm1@kernel.org>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patch.msgid.link/20260106044638.52906-1-superm1@kernel.org