drm/vc4: Unify PCM card's driver_name

User-space ALSA matches a card's driver name against an internal list of
aliases in order to select the correct configuration for the system.
When the driver name isn't defined, the match is performed against the
card's name.

With the introduction of RPi4 we now have two HDMI ports with two
distinct audio cards. This is reflected in their names, making them
different from previous RPi versions. With this, ALSA ultimately misses
the board's configuration on RPi4.

In order to avoid this, set "card->driver_name" to "vc4-hdmi"
unanimously.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
Fixes: f437bc1e ("drm/vc4: drv: Support BCM2711")
Reviewed-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20210115191209.12852-1-nsaenzjulienne@suse.de