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

Pull mailbox fixes from Jassi Brar:
 "Misc fixes for BCM mailbox driver

   - Fix build warnings by making static functions used within the file.
   - Check for potential NULL before dereferencing
   - Fix link error by defining HAS_DMA dependency"

* 'mailbox-devel' of git://git.linaro.org/landing-teams/working/fujitsu/integration:
  fix:mailbox:bcm-pdc-mailbox:mark symbols static where possible
  mailbox: bcm-pdc: potential NULL dereference in pdc_shutdown()
  mailbox: Add HAS_DMA Kconfig dependency to BCM_PDC_MBOX