bnxt_en: Deprecate support for legacy INTX mode

bnxt_en: Deprecate support for legacy INTX mode

Firmware has deprecated support for legacy INTX in 2022 (since v2.27)
and INTX hasn't been tested for many years before that.  INTX was
only used as a fallback mechansim in case MSIX wasn't available.  MSIX
is always supported by all firmware.  If MSIX capability in PCI config
space is not found during probe, abort.

Reviewed-by: Hongguang Gao <hongguang.gao@broadcom.com>
Reviewed-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Reviewed-by: Somnath Kotur <somnath.kotur@broadcom.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://patch.msgid.link/20240828183235.128948-5-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>