spi: zynq_qspi: Fixed incorrect return value error

This patch replaced "return 0" with "return status" to fix the
incorrect return value error reported by the coverity.

Reviewed-by: Michal Simek <michal.simek@xilinx.com>
Signed-off-by: Vipul Kumar <vipul.kumar@xilinx.com>
[jagan: rebased on master]
Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>