kbuild: remove redundant -rR flag of hdr-inst

Passing -rR for "make headers_install" is redundant because
the top Makefile has already set -rR to MAKEFLAGS.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>
diff --git a/scripts/Kbuild.include b/scripts/Kbuild.include
index 0f90981..353dcf0 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -186,10 +186,10 @@
 clean := -f $(srctree)/scripts/Makefile.clean obj
 
 ###
-# Shorthand for $(Q)$(MAKE) -rR -f scripts/Makefile.headersinst obj=
+# Shorthand for $(Q)$(MAKE) -f scripts/Makefile.headersinst obj=
 # Usage:
 # $(Q)$(MAKE) $(hdr-inst)=dir
-hdr-inst := -rR -f $(srctree)/scripts/Makefile.headersinst obj
+hdr-inst := -f $(srctree)/scripts/Makefile.headersinst obj
 
 # Prefix -I with $(srctree) if it is not an absolute path.
 # skip if -I has no parameter