serdev: Replace all instances of ENOTSUPP with EOPNOTSUPP

This replaces all instances of ENOTSUPP with EOPNOTSUPP since ENOTSUPP
is not a standard error code. This will help maintain consistency in
error codes when new serdev API's are added.

Signed-off-by: Neeraj Sanjay Kale <neeraj.sanjaykale@nxp.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>