nfp: flower: Remove usage of the deprecated ida_simple_xx() API

nfp: flower: Remove usage of the deprecated ida_simple_xx() API

ida_alloc() and ida_free() should be preferred to the deprecated
ida_simple_get() and ida_simple_remove().

This is less verbose.

Note that the upper bound of ida_alloc_range() is inclusive while the one
of ida_simple_get() was exclusive.
So NFP_FL_LAG_GROUP_MAX has been decreased by 1. It now better watch the
comment stating that "1 to 31 are valid".

The only other user of NFP_FL_LAG_GROUP_MAX has been updated accordingly in
nfp_fl_lag_put_unprocessed().

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>