bnxt_en: fix module unload sequence

bnxt_en: fix module unload sequence

Recent updates to the PTP part of bnxt changed the way PTP FIFO is
cleared, skbs waiting for TX timestamps are now cleared during
ndo_close() call. To do clearing procedure, the ptp structure must
exist and point to a valid address. Module destroy sequence had ptp
clear code running before netdev close causing invalid memory access and
kernel crash. Change the sequence to destroy ptp structure after device
close.

Fixes: 8f7ae5a85137 ("bnxt_en: improve TX timestamping FIFO configuration")
Reported-by: Taehee Yoo <ap420073@gmail.com>
Closes: https://lore.kernel.org/netdev/CAMArcTWDe2cd41=ub=zzvYifaYcYv-N-csxfqxUvejy_L0D6UQ@mail.gmail.com/
Signed-off-by: Vadim Fedorenko <vadfed@meta.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Michael Chan <michael.chan@broadcom.com>
Tested-by: Taehee Yoo <ap420073@gmail.com>
Link: https://patch.msgid.link/20250430170343.759126-1-vadfed@meta.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>