bpf: make bnxt compatible w/ bpf_xdp_adjust_tail

bpf: make bnxt compatible w/ bpf_xdp_adjust_tail

w/ bpf_xdp_adjust_tail helper xdp's data_end pointer could be changed as
well (only "decrease" of pointer's location is going to be supported).
changing of this pointer will change packet's size.
for bnxt driver we will just calculate packet's length unconditionally

Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Nikita V. Shirokov <tehnerd@tehnerd.com>
Acked-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
(cherry picked from commit b968e735c79767a3c91217fbae691581aa557d8d)
Orabug: 27988326

Signed-off-by: Somasundaram Krishnasamy <somasundaram.krishnasamy@oracle.com>
Reviewed-by: Brian Maly <brian.maly@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>