fm10k: free MBX IRQ before clearing interrupt scheme

During fm10k_io_error_detected we were clearing the interrupt scheme
before we freed the MBX IRQ. This causes a kernel panic because the MBX
IRQ are assigned after MSI-X initialization. Clearing the interrupt
scheme results in removing the MSI-X entry table. Fix this by freeing
the MBX IRQ before we clear the interrupt scheme, as we do elsewhere in
the driver.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Krishneil Singh <Krishneil.k.singh@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>