Merge branch 'mailbox-linux-4.1.y' of git://git.ti.com/rpmsg/mailbox into rproc-linux-4.1.y

Pull in the updated mailbox feature branch into the remoteproc tree
for adding support to the PRU-ICSS PRU cores in AM33xx and AM43xx
SoCs.

* 'mailbox-linux-4.1.y' of git://git.ti.com/rpmsg/mailbox

:
  ARM: dts: AM4372: Add PRUSS1 PRU mboxes to mailbox node
  ARM: dts: AM33xx: Add PRU mboxes to mailbox node

Signed-off-by: Suman Anna <s-anna@ti.com>