mailbox: bcm-flexrm-mailbox: add depends on ARCH_BCM_IPROC

The Broadcom FlexRM Mailbox is only present in the Broadcom IPROC SoCs.
Add depends on ARCH_BCM_IPROC to BCM_FLEXRX_MBOX.

Signed-off-by: Scott Branden <scott.branden@broadcom.com>
Reviewed-by: Ray Jui <ray.jui@broadcom.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/Kconfig

@@ -163,6 +163,7 @@ config BCM_PDC_MBOX
 config BCM_FLEXRM_MBOX
 	tristate "Broadcom FlexRM Mailbox"
 	depends on ARM64
+	depends on ARCH_BCM_IPROC || COMPILE_TEST
 	depends on HAS_DMA
 	select GENERIC_MSI_IRQ_DOMAIN
 	default ARCH_BCM_IPROC