arm64: defconfig: Add Broadcom Vulcan to defconfig

Enable Broadcom Vulcan support in arm64 default configuration. This will
build the device tree needed to boot on a Broadcom Vulcan board.

Signed-off-by: Jayachandran C <jchandra@broadcom.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm64/configs/defconfig

@@ -50,6 +50,7 @@ CONFIG_ARCH_SPRD=y
 CONFIG_ARCH_THUNDER=y
 CONFIG_ARCH_UNIPHIER=y
 CONFIG_ARCH_VEXPRESS=y
+CONFIG_ARCH_VULCAN=y
 CONFIG_ARCH_XGENE=y
 CONFIG_ARCH_ZYNQMP=y
 CONFIG_PCI=y