We should unlock if get_cxl_adapter() fails.

Fixes: 594ff7d0 ("cxl: Support to flash a new image on the adapter from a guest")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NFrederic Barrat <fbarrat@linux.vnet.ibm.com>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>