fpga: altera-cvp: Fix an error handling path in 'altera_cvp_probe()'

If 'fpga_mgr_create()' fails, we should release some resources, as done
in the other error handling path of the function.

Fixes: 7085e2a9 ("fpga: manager: change api, don't use drvdata")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Moritz Fischer <mdf@kernel.org>
Acked-by: Alan Tull <atull@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>