lib: dimlib: fix help text typos

Fix help text typos for DIMLIB.

Fixes: 4f75da36

 ("linux/dim: Move implementation to .c files")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Uwe Kleine-König <uwe@kleine-koenig.org>
Cc: Tal Gilboa <talgi@mellanox.com>
Cc: Saeed Mahameed <saeedm@mellanox.com>
Acked-by: Uwe Kleine-König <uwe@kleine-koenig.org>
Signed-off-by: David S. Miller <davem@davemloft.net>