treewide: remove explicit rules for *offsets.s

These explicit rules are unneeded because scripts/Makefile.build
provides a pattern rule to create %.s from %.c

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

samples/bpf/Makefile

@@ -227,9 +227,6 @@ $(LIBBPF): FORCE
 # Fix up variables inherited from Kbuild that tools/ build system won't like
 	$(MAKE) -C $(dir $@) RM='rm -rf' LDFLAGS= srctree=$(BPF_SAMPLES_PATH)/../../ O=
 
-$(obj)/syscall_nrs.s:	$(src)/syscall_nrs.c
-	$(call if_changed_dep,cc_s_c)
-
 $(obj)/syscall_nrs.h:	$(obj)/syscall_nrs.s FORCE
 	$(call filechk,offsets,__SYSCALL_NRS_H__)