libie: fix linking with libie_{adminq,fwlog} when CONFIG_LIBIE=n

Initially, libie contained only 1 module and I assumed that new modules
in its folder would depend on it.
However, Michał did a good job and libie_{adminq,fwlog} are completely
independent, but libie/ is still traversed by Kbuild only under
CONFIG_LIBIE != n.
This results in undefined references with certain kernel configs.

Tell Kbuild to always descend to libie/ to be able to build each module
regardless of whether the basic one is enabled.
If none of CONFIG_LIBIE* is set, Kbuild will just create an empty
built-in.a there with no side effects.

Fixes: 641585bc97 ("ixgbe: fwlog support for e610")
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/202509140606.j8z3rE73-lkp@intel.com
Reported-by: Breno Leitao <leitao@debian.org>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Closes: https://lore.kernel.org/CA+G9fYvH8d6pJRbHpOCMZFjgDCff3zcL_AsXL-nf5eB2smS8SA@mail.gmail.com
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Reviewed-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Reviewed-by: Vadim Fedorenko <vadim.fedorenko@linux.dev>
Link: https://patch.msgid.link/20250916160118.2209412-1-aleksander.lobakin@intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/ethernet/intel/Makefile

@@ -4,7 +4,7 @@
 #
 
 obj-$(CONFIG_LIBETH) += libeth/
-obj-$(CONFIG_LIBIE) += libie/
+obj-y += libie/
 
 obj-$(CONFIG_E100) += e100.o
 obj-$(CONFIG_E1000) += e1000/