ARM: Delete ARM11MPCore (ARM11 ARMv6K SMP) support

This ARM11 SMP configuration was one of the first SMP configurations
the ARM kernel supported, but it has the downside of odd DMA handling,
odd cache tagging, and often (as of recent) completely broken cache
handling on the ARM RealView PB11MPCore test chips. To boot the
platform it was necessary to completely disable the cache.
When it comes to the EB 11MPCore it is unclear if this ever worked.

These reference designs are now the only ARMv6K SMP platforms.

As only reference designs of purely academic interest remain, and
since the special-cased DMA and PMU code is hard to maintain and
doesn't really work, it is not really worth our time.

Delete the ARM11MPCore support along with:

- The special DMA quirk CONFIG_DMA_CACHE_RWFO that is only used
  on ARMv6K SMP, and we are the last ARMV6K system leaving the
  building and the cache handling is awkward, so good-bye.

- The special PMU handling that was only used by ARM11MPCore.

The following is left behind:

- TIMER_OF_DECLARE(arm_twd_11mp, "arm,arm11mp-twd-timer", ...)
  in arch/arm/kernel/smp_twd.c, this is still in use by Marvell MMP3
  arch/arm/boot/dts/marvell/mmp3.dtsi

- IRQCHIP_DECLARE(arm11mp_gic, "arm,arm11mp-gic", ...)
  in drivers/irqchip/irq-gic.c, this is still in use by Marvell MMP3
  arch/arm/boot/dts/marvell/mmp3.dtsi

- A compatible for the arm11mpcore SCU, since this was mistakedly
  used for the Cortex-A9 version of RealView EB.

These are unfortunate but will need to be kept around for
compatibility. New Marvell-specific compatibles should however probably
be added.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://lore.kernel.org/r/20231207-drop-11mpcore-v2-1-560b396f3bf5@linaro.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>