ARM: iop32x: mark as unused

The iop32x platform has recently been converted to be part of
the multiplatform configuration, and it should be possible to
keep it alive for longer by making it boot from devicetree like
we did for the related ixp4xx platform.

However, it appears that no users remain at this point, so just
mark the entire platform depending on CONFIG_UNUSED_BOARD_FILES,
with the intention of removing it in early 2023.

If any users remain, please speak up now.

Cc: Lennert Buytenhek <buytenh@wantstofly.org>
Acked-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

arch/arm/configs/iop32x_defconfig

@@ -9,6 +9,7 @@ CONFIG_MACH_GLANTANK=y
 CONFIG_ARCH_IQ80321=y
 CONFIG_ARCH_IQ31244=y
 CONFIG_MACH_N2100=y
+CONFIG_UNUSED_BOARD_FILES=y
 CONFIG_CMDLINE="console=ttyS0,115200 root=/dev/nfs ip=bootp cachepolicy=writealloc"
 CONFIG_FPE_NWFPE=y
 CONFIG_BINFMT_AOUT=y

arch/arm/mach-iop32x/Kconfig

@@ -3,7 +3,7 @@ menuconfig ARCH_IOP32X
 	bool "IOP32x-based platforms"
 	depends on ARCH_MULTI_V5
 	depends on CPU_LITTLE_ENDIAN
-	depends on ATAGS
+	depends on ATAGS && UNUSED_BOARD_FILES
 	select CPU_XSCALE
 	select GPIO_IOP
 	select GPIOLIB