dts: bcm2712: Drop snd_bcm2835 bootargs references from Pi5

Pi5 has no VCHIQ to support the snd_bcm2835 firmware audio
driver, so remove the reference to it from bootargs.

https://forums.raspberrypi.com/viewtopic.php?p=2219395#p2219395



Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>