arm64: defconfig: build snd_bcm2835 as module

arm64: defconfig: build snd_bcm2835 as module

Recently the VCHIQ driver which provides a kernel interface to the
BCM2835 VideoCore made a decent progress in staging. But the build
coverage is currently limited to bcm2835_defconfig (ARM 32 bit).
So build the most valueable driver which uses VCHIQ and enable
cinch audio support for Raspberry Pi on arm64.

Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Link: https://lore.kernel.org/r/20240414132052.11811-1-wahrenst@gmx.net
Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com>