parameters: only show possible enumerations if there are any
Enumeration values will only be shown if there are at least two of them.
With only one enumeration, it was just repeating what was previously printed
anyway.
Signed-off-by: Holger Schurig <holgerschurig@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>