kbuild: Do not run modules_install and install in paralel

Based on a x86-only patch by Andy Lutomirski <luto@amacapital.net>

With modular kernels, 'make install' is going to need the installed
modules at some point to generate the initramfs.
Signed-off-by: Michal Marek <mmarek@suse.cz>

Makefile

@@ -495,6 +495,12 @@ ifeq ($(KBUILD_EXTMOD),)
                 endif
         endif
 endif
+# install and module_install need also be processed one by one
+ifneq ($(filter install,$(MAKECMDGOALS)),)
+        ifneq ($(filter modules_install,$(MAKECMDGOALS)),)
+	        mixed-targets := 1
+        endif
+endif
 
 ifeq ($(mixed-targets),1)
 # ===========================================================================