platform/x86: dell-smbios: Introduce dispatcher for SMM calls

This splits up the dell-smbios driver into two drivers:
* dell-smbios
* dell-smbios-smm

dell-smbios can operate with multiple different dispatcher drivers to
perform SMBIOS operations.

Also modify the interface that dell-laptop and dell-wmi use align to this
model more closely.  Rather than a single global buffer being allocated
for all drivers, each driver will allocate and be responsible for it's own
buffer. The pointer will be passed to the calling function and each
dispatcher driver will then internally copy it to the proper location to
perform it's call.

Add defines for calls used by these methods in the dell-smbios.h header
for tracking purposes.

Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Reviewed-by: Edward O'Callaghan <quasisec@google.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

drivers/platform/x86/dell-wmi.c

@@ -638,13 +638,16 @@ static int dell_wmi_events_set_enabled(bool enable)
 	struct calling_interface_buffer *buffer;
 	int ret;
 
-	buffer = dell_smbios_get_buffer();
+	buffer = kzalloc(sizeof(struct calling_interface_buffer), GFP_KERNEL);
+	buffer->cmd_class = CLASS_INFO;
+	buffer->cmd_select = SELECT_APP_REGISTRATION;
 	buffer->input[0] = 0x10000;
 	buffer->input[1] = 0x51534554;
 	buffer->input[3] = enable;
-	dell_smbios_send_request(17, 3);
-	ret = buffer->output[0];
-	dell_smbios_release_buffer();
+	ret = dell_smbios_call(buffer);
+	if (ret == 0)
+		ret = buffer->output[0];
+	kfree(buffer);
 
 	return dell_smbios_error(ret);
 }