add a failing C test

tests/c-form/requests2.bpf.c

@@ -0,0 +1,18 @@
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+#include <bpf/bpf_core_read.h>
+
+char LICENSE[] SEC("license") = "GPL";
+
+SEC("kprobe/blk_mq_start_request")
+int example(struct pt_regs *ctx)
+{
+    u64 a = ctx->r15;
+    struct request *req = (struct request *)(ctx->di);
+    unsigned int something_ns = req->timeout;
+    unsigned int data_len = req->__data_len;
+    bpf_printk("data length %lld %ld %ld\n", data_len,  something_ns, a);
+
+    return 0;
+}