samples: bpf: Convert xdp_redirect_cpu_kern.o to XDP samples helper

Similar to xdp_monitor_kern, a lot of these BPF programs have been
reimplemented properly consolidating missing features from other XDP
samples. Hence, drop the unneeded code and rename to .bpf.c suffix.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210821002010.845777-18-memxor@gmail.com

samples/bpf/Makefile

@@ -165,7 +165,6 @@ always-y += tcp_tos_reflect_kern.o
 always-y += tcp_dumpstats_kern.o
 always-y += xdp_redirect_map_kern.o
 always-y += xdp_redirect_map_multi_kern.o
-always-y += xdp_redirect_cpu_kern.o
 always-y += xdp_rxq_info_kern.o
 always-y += xdp2skb_meta_kern.o
 always-y += syscall_tp_kern.o
@@ -356,6 +355,7 @@ endef
 
 CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
 
+$(obj)/xdp_redirect_cpu.bpf.o: $(obj)/xdp_sample.bpf.o
 $(obj)/xdp_redirect.bpf.o: $(obj)/xdp_sample.bpf.o
 $(obj)/xdp_monitor.bpf.o: $(obj)/xdp_sample.bpf.o
 
@@ -367,9 +367,10 @@ $(obj)/%.bpf.o: $(src)/%.bpf.c $(obj)/vmlinux.h $(src)/xdp_sample.bpf.h $(src)/x
 		-I$(srctree)/tools/lib $(CLANG_SYS_INCLUDES) \
 		-c $(filter %.bpf.c,$^) -o $@
 
-LINKED_SKELS := xdp_redirect.skel.h xdp_monitor.skel.h
+LINKED_SKELS := xdp_redirect_cpu.skel.h xdp_redirect.skel.h xdp_monitor.skel.h
 clean-files += $(LINKED_SKELS)
 
+xdp_redirect_cpu.skel.h-deps := xdp_redirect_cpu.bpf.o xdp_sample.bpf.o
 xdp_redirect.skel.h-deps := xdp_redirect.bpf.o xdp_sample.bpf.o
 xdp_monitor.skel.h-deps := xdp_monitor.bpf.o xdp_sample.bpf.o