libie: depend on DEBUG_FS when building LIBIE_FWLOG

libie: depend on DEBUG_FS when building LIBIE_FWLOG

LIBIE_FWLOG is unusable without DEBUG_FS. Mark it in Kconfig.

Fix build error on ixgbe when DEBUG_FS is not set. To not add another
layer of #if IS_ENABLED(LIBIE_FWLOG) in ixgbe fwlog code define debugfs
dentry even when DEBUG_FS isn't enabled. In this case the dummy
functions of LIBIE_FWLOG will be used, so not initialized dentry isn't a
problem.

Fixes: 641585bc978e ("ixgbe: fwlog support for e610")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Closes: https://lore.kernel.org/lkml/f594c621-f9e1-49f2-af31-23fbcb176058@roeck-us.net/
Signed-off-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Aleksandr Loktionov <aleksandr.loktionov@intel.com>
Tested-by: Rinitha S <sx.rinitha@intel.com> (A Contingent worker at Intel)
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20251104172333.752445-1-anthony.l.nguyen@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>