mailbox: add Tegra186 HSP driver

Tegra186's HSP module implements doorbells, mailboxes, semaphores, and
shared interrupts. This patch provides a driver for HSP, and hooks it
into the mailbox API. Currently, only doorbells are supported.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/mach-tegra/Kconfig b/arch/arm/mach-tegra/Kconfig
index b18a12e..f4affa5 100644
--- a/arch/arm/mach-tegra/Kconfig
+++ b/arch/arm/mach-tegra/Kconfig
@@ -56,8 +56,10 @@
 
 config TEGRA186
 	bool "Tegra186 family"
+	select DM_MAILBOX
 	select TEGRA186_GPIO
 	select TEGRA_ARMV8_COMMON
+	select TEGRA_HSP
 
 endchoice