greybus: operation: use dev_err in gb_operation_sync

Use the more informative dev_err in gb_operation_sync, which includes
the connection device name in the error message (which in turn encodes
the module, interface, bundle and cport ids).

Add missing braces to conditional-construct branches while at it.

Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>