arm: socfpga: mailbox: Add mailbox retry support

Resend mailbox command for 3 times with 2ms interval in between if
it receives MBOX_RESP_TIMEOUT and MBOX_RESP_DEVICE_BUSY response code.

Add a wrapper function mbox_send_cmd_common_retry() for retry, change
all the callers to use this wrapper function.

Signed-off-by: Ley Foon Tan <ley.foon.tan@intel.com>
Signed-off-by: Chee Hong Ang <chee.hong.ang@intel.com>