kdb: cleanup unused variables missed in the original kdb merge

The BTARGS and BTSYMARG variables do not have any function in the
mainline version of kdb.

Reported-by: Tim Bird <tim.bird@am.sony.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
diff --git a/kernel/debug/kdb/kdb_bt.c b/kernel/debug/kdb/kdb_bt.c
index 2f62fe8..7179eac 100644
--- a/kernel/debug/kdb/kdb_bt.c
+++ b/kernel/debug/kdb/kdb_bt.c
@@ -112,9 +112,8 @@
 	unsigned long addr;
 	long offset;
 
-	kdbgetintenv("BTARGS", &argcount);	/* Arguments to print */
-	kdbgetintenv("BTAPROMPT", &btaprompt);	/* Prompt after each
-						 * proc in bta */
+	/* Prompt after each proc in bta */
+	kdbgetintenv("BTAPROMPT", &btaprompt);
 
 	if (strcmp(argv[0], "bta") == 0) {
 		struct task_struct *g, *p;