configs: rpi_arm64: enable SDHCI BCMSTB driver

RPi5 have "brcm,bcm2712-sdhci" controller which is
handled by "sdhci-bcmstb" driver, so enable it.

Tested-by: Jens Maus <mail@jens-maus.de>
Tested-by: Darko Alavanja <darko.alavanja@konsulko.com>
Signed-off-by: Ivan T. Ivanov <iivanov@suse.de>
Signed-off-by: Matthias Brugger <mbrugger@suse.com>