mfd: core: Fix platform-device id generation

Make sure to always honour multi-function devices registered with
PLATFORM_DEVID_NONE (-1) or PLATFORM_DEVID_AUTO (-2) as id base. In this
case it does not make sense to append the cell id to the mfd-id base and
potentially change the requested behaviour.

Specifically this will allow multi-function devices to be registered
with PLATFORM_DEVID_AUTO while still having non-zero cell ids.

Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/mfd-core.c

@@ -125,9 +125,15 @@ static int mfd_add_device(struct device *parent, int id,
  struct platform_device *pdev;
  struct device_node *np = NULL;
  int ret = -ENOMEM;
+ int platform_id;
  int r;
 
- pdev = platform_device_alloc(cell->name, id + cell->id);
+ if (id < 0)
+ platform_id = id;
+ else
+ platform_id = id + cell->id;
+
+ pdev = platform_device_alloc(cell->name, platform_id);
  if (!pdev)
  goto fail_alloc;