selftests: bpf: centre kernel bpf objects under new subdir "progs"

At the moment, all kernel bpf objects are listed under BPF_OBJ_FILES.
Listing them manually sometimes causing patch conflict when people are
adding new testcases simultaneously.

It is better to centre all the related source files under a subdir
"progs", then auto-generate the object file list.

Suggested-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Jiong Wang <jiong.wang@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/testing/selftests/bpf/progs/sockmap_parse_prog.c

@@ -0,0 +1,46 @@
+#include <linux/bpf.h>
+#include "bpf_helpers.h"
+#include "bpf_util.h"
+#include "bpf_endian.h"
+
+int _version SEC("version") = 1;
+
+#define bpf_printk(fmt, ...)					\
+({								\
+	       char ____fmt[] = fmt;				\
+	       bpf_trace_printk(____fmt, sizeof(____fmt),	\
+				##__VA_ARGS__);			\
+})
+
+SEC("sk_skb1")
+int bpf_prog1(struct __sk_buff *skb)
+{
+	void *data_end = (void *)(long) skb->data_end;
+	void *data = (void *)(long) skb->data;
+	__u32 lport = skb->local_port;
+	__u32 rport = skb->remote_port;
+	__u8 *d = data;
+	__u32 len = (__u32) data_end - (__u32) data;
+	int err;
+
+	if (data + 10 > data_end) {
+		err = bpf_skb_pull_data(skb, 10);
+		if (err)
+			return SK_DROP;
+
+		data_end = (void *)(long)skb->data_end;
+		data = (void *)(long)skb->data;
+		if (data + 10 > data_end)
+			return SK_DROP;
+	}
+
+	/* This write/read is a bit pointless but tests the verifier and
+	 * strparser handler for read/write pkt data and access into sk
+	 * fields.
+	 */
+	d = data;
+	d[7] = 1;
+	return skb->len;
+}
+
+char _license[] SEC("license") = "GPL";