can: mcp251xfd: mcp251xfd_register_get_dev_id(): fix return of error value

Clang static analysis reports this issue:

| mcp251xfd-core.c:1813:7: warning: The left operand
|   of '&' is a garbage value
|   FIELD_GET(MCP251XFD_REG_DEVID_ID_MASK, dev_id),
|   ^                                      ~~~~~~

dev_id is set in a successful call to mcp251xfd_register_get_dev_id().
Though the status of calls made by mcp251xfd_register_get_dev_id() are
checked and handled, their status' are not returned. So return err.

Fixes: 55e5b97f00 ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
Link: https://lore.kernel.org/all/20220319153128.2164120-1-trix@redhat.com
Signed-off-by: Tom Rix <trix@redhat.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/spi/mcp251xfd/mcp251xfd-core.c

@@ -1786,7 +1786,7 @@ mcp251xfd_register_get_dev_id(const struct mcp251xfd_priv *priv, u32 *dev_id,
  out_kfree_buf_rx:
 	kfree(buf_rx);
 
-	return 0;
+	return err;
 }
 
 #define MCP251XFD_QUIRK_ACTIVE(quirk) \