ix(4): Add support for firmware logging for E610 adapters

This is part 3 of the support for the new Intel Ethernet E610
family of devices

The ix driver now enables firmware logging on Intel E610 devices
for debugging with Customer Support. Logs are enabled by default
and generated in binary format that requires decoding by support
teams. The collected data is firmware and hardware related for
debugging purposes only.

When the driver loads, it creates a fw_log sysctl node under the
debug section. Events are organized into categories (modules) for
targeted logging, and users can adjust verbosity levels as needed.

This adds sysctl support for the firmware logging feature and
updates the ix(4) manual page with documentation.

Signed-off-by: Yogesh Bhosale <yogesh.bhosale@intel.com>
Co-developed-by: Krzysztof Galazka <krzysztof.galazka@intel.com>

Reviewed by:	ziaee, kbowling
Tested by:      Mateusz Moga <mateusz.moga@intel.com>
MFC after:      1 weeks
Sponsored by:   Intel Corporation
Differential Revision:	https://reviews.freebsd.org/D53973

share/man/man4/ix.4

@@ -138,7 +138,7 @@ The
 driver supports the following
 .Xr sysctl 8
 variables:
-.Bl -tag -width "dev.ix.?.debug.dump.clusters"
+.Bl -tag -width "dev.ix.?.debug.fw_log.severity.<module>"
 .It Va dev.ix.?.debug.dump.clusters
 Specify a bitmask to select firmware event clusters
 to be included in the debug dump.
@@ -160,6 +160,38 @@ Output must be redirected to a file
 and decoded by Intel Customer Support.
 .Pp
 This feature is only supported on E610.
+.It Va dev.ix.?.debug.fw_log.severity.<module>
+Specify firmware logging verbosity level for the specified module.
+Available levels include:
+.Pp
+.Bl -tag -compact
+.It 0
+none
+.It 1
+error
+.It 2
+warning
+.It 3
+normal
+.It 4
+verbose
+.El
+.Pp
+Supported modules: general, ctrl, link, link_topo, dnl, i2c, sdp, mdio,
+adminq, hdma, lldp, dcbx, dcb, xlr, nvm, auth, vpd, iosf, parser, sw,
+scheduler, txq, acl, post, watchdog, task_dispatch, mng, synce, health,
+tsdrv, pfreg, mdlver.
+.Pp
+This feature is only supported on E610 devices.
+.It Va dev.ix.?.debug.fw_log.register
+Specify 1 to apply per-device firmware logging configuration.
+.Pp
+This feature is only supported on E610 devices.
+.It Va dev.ix.?.debug.fw_log.on_load
+Enable firmware logging during driver initialization when set via
+.Xr kenv 1 .
+.Pp
+This feature is only supported on E610 devices.
 .El
 .Sh DIAGNOSTICS
 .Bl -diag