kbuild: generate generic headers before recursing into scripts

The headers are now needed inside scripts/mod since 6543bec
("mod/file2alias: make modalias generation safe for cross compiling").

Reported-and-tested-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Reported-and-tested-by: "Jon Medhurst (Tixy)" <tixy@linaro.org>
Signed-off-by: Andreas Schwab <schwab@linux-m68k.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>

Makefile

@@ -513,7 +513,8 @@ ifeq ($(KBUILD_EXTMOD),)
 # Carefully list dependencies so we do not try to build scripts twice
 # in parallel
 PHONY += scripts
-scripts: scripts_basic include/config/auto.conf include/config/tristate.conf
+scripts: scripts_basic include/config/auto.conf include/config/tristate.conf \
+	 asm-generic
 	$(Q)$(MAKE) $(build)=$(@)
 
 # Objects we will link into vmlinux / subdirs we need to visit