From: Lubomir Rintel

This adds a driver for mailbox IPC mechanism present on Broadcom
BCM2835 SoC, used in Raspberry Pi and Roku 2 devices.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Craig McGeachie <slapdau@yahoo.com.au>
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Changes made since v1:
 * Re-position memory barriers in accordance with the advice from
   section 1.3 of the BCM2835 Arm Peripherals document.
 * Even if the caller wishes to discard the reply, wait for it anyway
   to prevent incorrect correlation of requests and replies.
 * Replace of_ioremap() call with devm_request_and_ioremap().
 * Update device tree in line with documentation.
 * Invoke INIT_COMPLETION before re-using the channel completion.
Merge branch 'board-mailbox' of github.com:rickytarr/linux into board-mailbox

Missed a file and need to clean up.