kbuild: move asm-offsets.h to include/generated

The simplest method was to add an extra asm-offsets.h
file in arch/$ARCH/include/asm that references the generated file.

We can now migrate the architectures one-by-one to reference
the generated file direct - and when done we can delete the
temporary arch/$ARCH/include/asm/asm-offsets.h file.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/arch/um/Makefile b/arch/um/Makefile
index fc633db..fab8121 100644
--- a/arch/um/Makefile
+++ b/arch/um/Makefile
@@ -149,6 +149,6 @@
 
 $(SHARED_HEADERS)/kern_constants.h:
 	$(Q)mkdir -p $(dir $@)
-	$(Q)echo '#include "../../../../include/asm/asm-offsets.h"' >$@
+	$(Q)echo '#include "../../../../include/generated/asm-offsets.h"' >$@
 
 export SUBARCH USER_CFLAGS CFLAGS_NO_HARDENING OS HEADER_ARCH DEV_NULL_PATH