openvswitch: Fix flow lookup to use unmasked key

The commit mentioned below causes the ovs_flow_tbl_lookup() function
to be called with the masked key. However, it's supposed to be called
with the unmasked key. This due to the fact that the datapath supports
installing wider flows, and OVS relies on this behavior. For example
if ipv4(src=1.1.1.1/192.0.0.0, dst=1.1.1.2/192.0.0.0) exists, a wider
flow (smaller mask) of ipv4(src=192.1.1.1/128.0.0.0,dst=192.1.1.2/
128.0.0.0) is allowed to be added.

However, if we try to add a wildcard rule, the installation fails:

$ ovs-appctl dpctl/add-flow system@myDP "in_port(1),eth_type(0x0800), \
  ipv4(src=1.1.1.1/192.0.0.0,dst=1.1.1.2/192.0.0.0,frag=no)" 2
$ ovs-appctl dpctl/add-flow system@myDP "in_port(1),eth_type(0x0800), \
  ipv4(src=192.1.1.1/0.0.0.0,dst=49.1.1.2/0.0.0.0,frag=no)" 2
ovs-vswitchd: updating flow table (File exists)

The reason is that the key used to determine if the flow is already
present in the system uses the original key ANDed with the mask.
This results in the IP address not being part of the (miniflow) key,
i.e., being substituted with an all-zero value. When doing the actual
lookup, this results in the key wrongfully matching the first flow,
and therefore the flow does not get installed.

This change reverses the commit below, but rather than having the key
on the stack, it's allocated.

Fixes: 190aa3e7 ("openvswitch: Fix Frame-size larger than 1024 bytes warning.")

Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>