kernel: Add mailbox and LPC drivers

Mailbox and LPC drivers:

 drivers/mailbox: Add Aspeed mailbox driver
 drivers/misc: Add Aspeed LPC control driver
 dt-bindings: Add Aspeed LPC Control bindings
 dt-bindings: Add Aspeed mailbox bindings

Enable the devices for Zaius and Witherspoon:

 ARM: dts: aspeed-bmc-opp-witherspoon: Enable mailbox and LPC control
 ARM: dts: aspeed-bmc-opp-zaius: Enable mailbox and LPC control node
 ARM: dts: aspeed-g5: Add mailbox and LPC control node

Change-Id: I8030404c5c2f6d90935bbd6b26de7143f564f06d
Signed-off-by: Joel Stanley <joel@jms.id.au>
diff --git a/common/recipes-kernel/linux/linux-obmc_4.7.bb b/common/recipes-kernel/linux/linux-obmc_4.7.bb
index f970984..f862ee8 100644
--- a/common/recipes-kernel/linux/linux-obmc_4.7.bb
+++ b/common/recipes-kernel/linux/linux-obmc_4.7.bb
@@ -1,6 +1,6 @@
 KBRANCH ?= "dev-4.7"
 LINUX_VERSION ?= "4.7"
 
-SRCREV="b40fcf1208470a9107caaf7e73387799f32c5111"
+SRCREV="26d51e63ed7433662b0137dff63b42d6969417d5"
 
 require linux-obmc.inc