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>

scripts/Kbuild.include

@@ -186,10 +186,10 @@ modbuiltin := -f $(srctree)/scripts/Makefile.modbuiltin obj
 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