kbuild: remove unused RANLIB

RANLIB was added by commit e2211743 (more than a decade ago)
but it has been never referenced at all.
Signed-off-by: NMasahiro Yamada <yamada.m@jp.panasonic.com>

Makefile

@@ -354,7 +354,6 @@ STRIP		= $(CROSS_COMPILE)strip
 OBJCOPY		= $(CROSS_COMPILE)objcopy
 OBJDUMP		= $(CROSS_COMPILE)objdump
 AWK		= awk
-RANLIB		= $(CROSS_COMPILE)RANLIB
 DTC		= dtc
 CHECK		= sparse