brcmfmac: send mailbox interrupt twice for specific hardware device

For PCIE wireless device with core revision less than 14, device may miss
PCIE to System Backplane Interrupt via PCIEtoSBMailbox. So add sending
mail box interrupt twice as a hardware workaround.

Signed-off-by: Wright Feng <wright.feng@cypress.com>
Reviewed-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>