HID: bpf: error on warnings when compiling bpf objects

There is no real reasons to paper over warnings for such small programs.

Link: https://lore.kernel.org/r/20240608-hid_bpf_struct_ops-v3-13-6ac6ade58329@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

drivers/hid/bpf/progs/Makefile

@@ -56,7 +56,7 @@ clean:
 
 %.bpf.o: %.bpf.c vmlinux.h $(BPFOBJ) | $(OUTPUT)
 	$(call msg,BPF,$@)
-	$(Q)$(CLANG) -g -O2 --target=bpf $(INCLUDES)			      \
+	$(Q)$(CLANG) -g -O2 --target=bpf -Wall -Werror $(INCLUDES)	      \
 		 -c $(filter %.c,$^) -o $@ &&				      \
 	$(LLVM_STRIP) -g $@