kbuild: move "quote" to Kbuild.include to be consistent

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 547e15d..2ec6829 100644
--- a/scripts/Kbuild.include
+++ b/scripts/Kbuild.include
@@ -3,6 +3,7 @@
 
 # Convenient variables
 comma   := ,
+quote   := "
 squote  := '
 empty   :=
 space   := $(empty) $(empty)