sfc: Increase MCDI status timeout to 250ms

The SFC9120 MC firmware often takes longer than 20ms to reboot and
update the warm boot count in BIU_MC_SFT_STATUS_REG.  A timeout of
250ms is very generous for an MC reboot.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/mcdi.c

@@ -27,10 +27,10 @@
 
 /* A reboot/assertion causes the MCDI status word to be set after the
  * command word is set or a REBOOT event is sent. If we notice a reboot
- * via these mechanisms then wait 20ms for the status word to be set.
+ * via these mechanisms then wait 250ms for the status word to be set.
  */
 #define MCDI_STATUS_DELAY_US		100
-#define MCDI_STATUS_DELAY_COUNT		200
+#define MCDI_STATUS_DELAY_COUNT		2500
 #define MCDI_STATUS_SLEEP_MS						\
 	(MCDI_STATUS_DELAY_US * MCDI_STATUS_DELAY_COUNT / 1000)