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

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: 55e5b97f003e ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
Link: https://lore.kernel.org/all/[email protected]
Signed-off-by: Tom Rix <[email protected]>
Signed-off-by: Marc Kleine-Budde <[email protected]>