nvmem: Do not expect fixed layouts to grab a layout driver

Two series lived in parallel for some time, which led to this situation:
- The nvmem-layout container is used for dynamic layouts
- We now expect fixed layouts to also use the nvmem-layout container but
this does not require any additional driver, the support is built-in the
nvmem core.

Ensure we don't refuse to probe for wrong reasons.

Fixes: 27f699e5 ("nvmem: core: add support for fixed cells *layout*")
Cc: stable@vger.kernel.org
Reported-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Tested-by: Rafał Miłecki <rafal@milecki.pl>
Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

Link: https://lore.kernel.org/r/20231124193814.360552-1-miquel.raynal@bootlin.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/nvmem/core.c

@@ -796,6 +796,12 @@ static struct nvmem_layout *nvmem_layout_get(struct nvmem_device *nvmem)
 	if (!layout_np)
 		return NULL;
 
+	/* Fixed layouts don't have a matching driver */
+	if (of_device_is_compatible(layout_np, "fixed-layout")) {
+		of_node_put(layout_np);
+		return NULL;
+	}
+
 	/*
 	 * In case the nvmem device was built-in while the layout was built as a
 	 * module, we shall manually request the layout driver loading otherwise