astbmc: Fail SFC init if SIO is unavailable

If SuperIO is unavailable then the driver cannot perform accesses on
which it currently depends. Test for SuperIO availability during
initialsation and bail out immediately if it is absent.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

hw/ast-bmc/ast-sf-ctrl.c

@@ -948,6 +948,9 @@ int ast_sf_open(uint8_t type, struct spi_flash_ctrl **ctrl)
 	struct ast_sf_ctrl *ct;
 #ifdef __SKIBOOT__
 	uint32_t hicr7;
+
+	if (!ast_sio_is_enabled())
+		return -ENODEV;
 #endif /* __SKIBOOT__ */
 
 	if (type != AST_SF_TYPE_PNOR && type != AST_SF_TYPE_BMC