selftests: drv-net: rss_ctx: test RSS contexts persist after ifdown/up

selftests: drv-net: rss_ctx: test RSS contexts persist after ifdown/up

Add a test to verify that RSS contexts persist across interface
down/up along with their associated Ntuple filters. Another test
that creates contexts/rules keeping interface down and test their
persistence is also added.

Tested on bnxt_en:

 TAP version 13
 1..1
 # timeout set to 0
 # selftests: drivers/net/hw: rss_ctx.py
 # TAP version 13
 # 1..2
 # ok 1 rss_ctx.test_rss_context_persist_create_and_ifdown
 # ok 2 rss_ctx.test_rss_context_persist_ifdown_and_create # SKIP Create context not supported with interface down
 # # Totals: pass:1 fail:0 xfail:0 xpass:0 skip:1 error:0

Reviewed-by: Andy Gospodarek <andrew.gospodarek@broadcom.com>
Signed-off-by: Pavan Chebbi <pavan.chebbi@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20260219185313.2682148-4-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>