mlxsw: spectrum_matchall: Process matchall events from the same cb as flower

Currently there are two callbacks registered: one for matchall,
one for flower. This causes the user to see "in_hw_count 2" in TC filter
dump. Because of this and also as a preparation for future matchall
offload for rules equivalent to flower-all-match, move the processing of
shared block into matchall.c. Leave only one cb for mlxsw driver
per-block.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>