ARM: 9285/1: remove meaningless arch/arm/mach-rda/Makefile

You do not need to put Makefile if there is nothing to compile.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

arch/arm/Makefile

@@ -213,7 +213,6 @@ machine-$(CONFIG_ARCH_OMAP2PLUS)	+= omap2
 machine-$(CONFIG_ARCH_ORION5X)		+= orion5x
 machine-$(CONFIG_ARCH_PXA)		+= pxa
 machine-$(CONFIG_ARCH_QCOM)		+= qcom
-machine-$(CONFIG_ARCH_RDA)		+= rda
 machine-$(CONFIG_ARCH_REALTEK)		+= realtek
 machine-$(CONFIG_ARCH_ROCKCHIP)		+= rockchip
 machine-$(CONFIG_ARCH_RPC)		+= rpc

arch/arm/mach-rda/Makefile

-# SPDX-License-Identifier: GPL-2.0-only
-obj- += dummy.o