octeontx2-af: Remove unnecessary devm_kfree

Remove devm_kfree of memory where VLAN entry to RVU PF mapping
info is saved. This will be freed anyway at driver exit.
Having this could result in warning from devm_kfree() if
the memory is not allocated due to errors in rvu_nix_block_init()
before nix_setup_txvlan().

Fixes: 9a946def ("octeontx2-af: Modify nix_vtag_cfg mailbox to support TX VTAG entries")
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>