sepolicy: Apply dhcpcd sepolicy to dhcpcd-6.8.2

Apply the same sepolicy used on dhcpcd to dhcpcd-6.8.2,
which is have it run with the dhcp context, and have its
data files possess the dhcp_data_file context.

BUG: 22956197
Change-Id: I7915b694038bb309d93691ef5d4d293593ef3b5e