mailbox: Add HAS_DMA Kconfig dependency to BCM_PDC_MBOX

Add HAS_DMA Kconfig dependency to BCM_PDC_MBOX to avoid link
error on some platforms.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Rob Rice <rrice@broadcom.com>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/Kconfig

@@ -127,6 +127,7 @@ config XGENE_SLIMPRO_MBOX
 config BCM_PDC_MBOX
 	tristate "Broadcom PDC Mailbox"
 	depends on ARM64 || COMPILE_TEST
+	depends on HAS_DMA
 	default ARCH_BCM_IPROC
 	help
 	  Mailbox implementation for the Broadcom PDC ring manager,