cfg80211: fix CONFIG_CFG80211_EXTRA_REGDB_KEYDIR typo

The kbuild change here accidentally removed not only the
unquoting, but also the last character of the variable
name. Fix that.

Fixes: 129ab0d2 ("kbuild: do not quote string values in include/config/auto.conf")
Reviewed-by: Masahiro Yamada <masahiroy@kernel.org>
Link: https://lore.kernel.org/r/20220221155512.1d25895f7c5f.I50fa3d4189fcab90a2896fe8cae215035dae9508@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/wireless/Makefile

@@ -33,7 +33,7 @@ $(obj)/shipped-certs.c: $(wildcard $(srctree)/$(src)/certs/*.hex)
 	  echo 'unsigned int shipped_regdb_certs_len = sizeof(shipped_regdb_certs);'; \
 	 ) > $@
 
-$(obj)/extra-certs.c: $(CONFIG_CFG80211_EXTRA_REGDB_KEYDI) \
+$(obj)/extra-certs.c: $(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR) \
 		      $(wildcard $(CONFIG_CFG80211_EXTRA_REGDB_KEYDIR)/*.x509)
 	@$(kecho) "  GEN     $@"
 	$(Q)(set -e; \