mailbox: config: ti-msgmgr: Default set to ARCH_K3 for TI msg manager

Defaulting the build to ARCH_K3 for the TI message manager driver.
Signed-off-by: Nicolas Frayer <nfrayer@baylibre.com>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/Kconfig

@@ -136,6 +136,7 @@ config STI_MBOX
 config TI_MESSAGE_MANAGER
 	tristate "Texas Instruments Message Manager Driver"
 	depends on ARCH_KEYSTONE || ARCH_K3
+	default ARCH_K3
 	help
 	  An implementation of Message Manager slave driver for Keystone
 	  and K3 architecture SoCs from Texas Instruments. Message Manager