octeontx2-af: Delete NIX_RXVLAN_ALLOC mailbox message

Since mailbox message for installing flows is in place,
remove the RXVLAN_ALLOC mbox message which is redundant.

Signed-off-by: Subbaraya Sundeep <sbhatta@marvell.com>
Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
Signed-off-by: Naveen Mamindlapalli <naveenm@marvell.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>