Moved the setting of 'DEV_RX_OFFLOAD_JUMBO_FRAME' from
'cmd_config_max_pkt_len_parsed()' to 'init_config()' caused fail the case
where 'max_rx_pkt_len' is changed from the command line via
"port config all max-pkt-len".

The 'init_config()' function is only called when testpmd is started,
but the DEV_RX_OFFLOAD_JUMBO_FRAME setting needs to be recomputed whenever
'max_rx_pkt_len' changes.

Define the 'update_jumbo_frame_offload()' function for both 'init_config()'
and 'cmd_config_max_pkt_len_parsed()', and detect if 'max_rx_pkt_len'
should be update to 1500 + overhead as default configuration. At the same
time, the offloads of rx queue also should update the value once port
offloads changed (e.g.: disabled JUMBO_FRAME offload via changed
max-pkt-len, reproduce steps [1]), otherwise, it would cause unexpected
result.

[1]
--------------------------------------------------------------------------
./x86_64-native-linuxapp-gcc/app/dpdk-testpmd  -c 0xf -n 4  -- -i
    --max-pkt-len=9000 --tx-offloads=0x8000 --rxq=4 --txq=4 --disable-rss
testpmd>  set verbose 3
testpmd>  port stop all
testpmd>  port config all max-pkt-len 1518  port start all

// Got fail error info without this patch
Configuring Port 0 (socket 1)
Ethdev port_id=0 rx_queue_id=0, new added offloads 0x800 must be
within per-queue offload capabilities 0x0 in rte_eth_rx_queue_setup()
Fail to configure port 0 rx queues //<-- Fail error info;
--------------------------------------------------------------------------

Fixes: 761c4d6690 ("app/testpmd: fix max Rx packet length for VLAN packets")

Signed-off-by: Steve Yang <redacted>
---
 app/test-pmd/cmdline.c    |  1 +
 app/test-pmd/parameters.c |  1 +
 app/test-pmd/testpmd.c    | 63 ++++++++++++++++++++++++++++-----------
 app/test-pmd/testpmd.h    |  2 ++
 4 files changed, 50 insertions(+), 17 deletions(-)

diff --git a/app/test-pmd/cmdline.c b/app/test-pmd/cmdline.c
index 89034c8b72..8b6b7b6206 100644
--- a/app/test-pmd/cmdline.c
+++ b/app/test-pmd/cmdline.c

@@ -1901,6 +1901,7 @@ cmd_config_max_pkt_len_parsed(void *parsed_result,
                        printf("Unknown parameter\n");
                        return;
                }
+               update_jumbo_frame_offload(pid, false);