llkd: add ro.llk.sysrq_t

Allow sysrq stack trace dump to be disabled by ro.llk.sysrq_t.

Default is true if not on a limited memory device ro.config.low_ram.
Value is true if the property value is "eng" and on a userdebug or
eng device, signaled by the ro.debuggable set to 1.

Test: compile
Bug: 118712403
Change-Id: I02e999dc640125b6a08dca10077716e5d006da49
diff --git a/llkd/include/llkd.h b/llkd/include/llkd.h
index cb56f34..b16b1d8 100644
--- a/llkd/include/llkd.h
+++ b/llkd/include/llkd.h
@@ -35,6 +35,8 @@
 #define LLK_ENABLE_DEFAULT             false /* "eng" and userdebug true */
 #define KHT_ENABLE_WRITEABLE_PROPERTY  "khungtask.enable"
 #define KHT_ENABLE_PROPERTY            "ro." KHT_ENABLE_WRITEABLE_PROPERTY
+#define LLK_ENABLE_SYSRQ_T_PROPERTY    "ro.llk.sysrq_t"
+#define LLK_ENABLE_SYSRQ_T_DEFAULT     true
 #define LLK_MLOCKALL_PROPERTY          "ro.llk.mlockall"
 #define LLK_MLOCKALL_DEFAULT           true
 #define LLK_KILLTEST_PROPERTY          "ro.llk.killtest"