selftests/hid: do not manually call headers_install

"make headers" is a requirement before calling make on the selftests
dir, so we should not have to manually install those headers

Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Tested-by: Nick Desaulniers <ndesaulniers@google.com> # Build
Tested-by: Justin Stitt <justinstitt@google.com>
Link: https://lore.kernel.org/r/20230825-wip-selftests-v3-2-639963c54109@kernel.org
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>

tools/testing/selftests/hid/Makefile

@@ -21,7 +21,7 @@ CXX ?= $(CROSS_COMPILE)g++
 
 HOSTPKG_CONFIG := pkg-config
 
-CFLAGS += -g -O0 -rdynamic -Wall -Werror -I$(KHDR_INCLUDES) -I$(OUTPUT)
+CFLAGS += -g -O0 -rdynamic -Wall -Werror -I$(OUTPUT)
 LDLIBS += -lelf -lz -lrt -lpthread
 
 # Silence some warnings when compiled with clang
@@ -65,7 +65,6 @@ BPFTOOLDIR := $(TOOLSDIR)/bpf/bpftool
 SCRATCH_DIR := $(OUTPUT)/tools
 BUILD_DIR := $(SCRATCH_DIR)/build
 INCLUDE_DIR := $(SCRATCH_DIR)/include
-KHDR_INCLUDES := $(SCRATCH_DIR)/uapi/include
 BPFOBJ := $(BUILD_DIR)/libbpf/libbpf.a
 ifneq ($(CROSS_COMPILE),)
 HOST_BUILD_DIR		:= $(BUILD_DIR)/host
@@ -151,9 +150,6 @@ else
 	$(Q)cp "$(VMLINUX_H)" $@
 endif
 
-$(KHDR_INCLUDES)/linux/hid.h: $(top_srcdir)/include/uapi/linux/hid.h
-	$(MAKE) -C $(top_srcdir) INSTALL_HDR_PATH=$(SCRATCH_DIR)/uapi headers_install
-
 $(RESOLVE_BTFIDS): $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/resolve_btfids	\
 		       $(TOOLSDIR)/bpf/resolve_btfids/main.c	\
 		       $(TOOLSDIR)/lib/rbtree.c			\
@@ -231,7 +227,7 @@ $(BPF_SKELS): %.skel.h: %.bpf.o $(BPFTOOL) | $(OUTPUT)
 	$(Q)$(BPFTOOL) gen object $(<:.o=.linked1.o) $<
 	$(Q)$(BPFTOOL) gen skeleton $(<:.o=.linked1.o) name $(notdir $(<:.bpf.o=)) > $@
 
-$(OUTPUT)/%.o: %.c $(BPF_SKELS) $(KHDR_INCLUDES)/linux/hid.h
+$(OUTPUT)/%.o: %.c $(BPF_SKELS)
 	$(call msg,CC,,$@)
 	$(Q)$(CC) $(CFLAGS) -c $(filter %.c,$^) $(LDLIBS) -o $@