Remove Use_lmkd_stats_log from build

Use_lmkd_stats_log used to control LMKD_LOG_STATS when compiling lmkd.

However, for newer Android releases, we mandate that lmkd informs statsd of process kills (change id I8cb123b9488fbc6e88863c2f0e75f1422bcd282e)
After aosp/1555318 we compile lmkd with statsd by default, so this setting is a noop.

Change-Id: I91bd08198fe2275fb8aca77ae5ea637df360d416
Test: build
Bug: 177985094
diff --git a/core/soong_config.mk b/core/soong_config.mk
index fde5832..fd8d3e4 100644
--- a/core/soong_config.mk
+++ b/core/soong_config.mk
@@ -159,7 +159,6 @@
 $(call add_json_bool, Check_elf_files,                   $(filter true,$(PRODUCT_CHECK_ELF_FILES)))
 
 $(call add_json_bool, Uml,                               $(filter true,$(TARGET_USER_MODE_LINUX)))
-$(call add_json_bool, Use_lmkd_stats_log,                $(filter true,$(TARGET_LMKD_STATS_LOG)))
 $(call add_json_str,  VendorPath,                        $(TARGET_COPY_OUT_VENDOR))
 $(call add_json_str,  OdmPath,                           $(TARGET_COPY_OUT_ODM))
 $(call add_json_str,  VendorDlkmPath,                    $(TARGET_COPY_OUT_VENDOR_DLKM))