am62x|am62p: enable AVB for vendor_dlkm partition
When we enable vendor_dlkm partition we forgot to support AVB on it.
So add AVB variable to enable it on vendor_dlkm and create new vbmeta partition for vendor_dlkm.
Fixes: 93cd234f ("all: enable vendor_dlkm partition") Signed-off-by: Guillaume La Roque glaroque@baylibre.com