Merge branch 'mailbox-devel' of git://git.linaro.org/landing-teams/working/fujitsu/integration

Pull mailbox framework updates from Jassi Brar.

* 'mailbox-devel' of git://git.linaro.org/landing-teams/working/fujitsu/integration:
  mailbox: Add Altera mailbox driver
  mailbox: check for bit set before polling
  Mailbox: Fix return value check in pcc_init()