net: mvpp2: Don't use dynamic allocs for local variables

Some helper functions that search for given entries in the TCAM filter
on PPv2 controller make use of dynamically alloced temporary variables,
allocated with GFP_KERNEL. These functions can be called in atomic
context, and dynamic alloc is not really needed in these cases anyways.

This commit gets rid of dynamic allocs and use stack allocation in the
following functions, and where they're used :
 - mvpp2_prs_flow_find
 - mvpp2_prs_vlan_find
 - mvpp2_prs_double_vlan_find
 - mvpp2_prs_mac_da_range_find

For all these functions, instead of returning an temporary object
representing the TCAM entry, we simply return the TCAM id that matches
the requested entry.
Signed-off-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>