x86, intel-mid: Return proper error code from get_gpio_by_name()

This patch cleans up get_gpio_by_name() to return an error code
instead of hardcoded -1.

Signed-off-by: David Cohen <david.a.cohen@linux.intel.com>
Link: http://lkml.kernel.org/r/1389913624-9149-4-git-send-email-david.a.cohen@linux.intel.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/platform/intel-mid/sfi.c

@@ -224,7 +224,7 @@ int get_gpio_by_name(const char *name)
 		if (!strncmp(name, pentry->pin_name, SFI_NAME_LEN))
 			return pentry->pin_no;
 	}
-	return -1;
+	return -EINVAL;
 }
 
 void __init intel_scu_device_register(struct platform_device *pdev)