platform/x86: dell-smbios-wmi: make function dell_smbios_wmi_call static

The function dell_smbios_wmi_call is local to the source and does not
need to be in global scope, so make it static.

Cleans up sparse warning:
symbol 'dell_smbios_wmi_call' was not declared. Should it be static?
Signed-off-by: NColin Ian King <colin.king@canonical.com>
Acked-by: NMario Limonciello <mario.limonciello@dell.com>
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/dell-smbios-wmi.c

@@ -82,7 +82,7 @@ static int run_smbios_call(struct wmi_device *wdev)
 	return 0;
 }
 
-int dell_smbios_wmi_call(struct calling_interface_buffer *buffer)
+static int dell_smbios_wmi_call(struct calling_interface_buffer *buffer)
 {
 	struct wmi_smbios_priv *priv;
 	size_t difference;