ARM: rework ARM11 CPU selection logic

Support for SMP on ARM1136r0 has been broken for a while, and nobody
is working on fixing it. I had a plan to change ARMv6 support to no
longer coexist in a common kernel with ARMv7 CPUs but instead ARMv5 and
below. This would have addressed the problem, but after a recent mailing
list discussion, we concluded that an easier approach is to just forbid
ARM1136r0 CPU support on SMP-enabled kernels.

This mainly affects users of the Nokia N800/N810 tablets using an
OMAP2420 SoC, which is the only commercial product with an ARM1136r0
that is still supported by the kernel.

The other machines that are still in the same hardware catogory are:

 - TI OMAP2420 H4 reference board
 - TI OMAP2430 SDP software development platform
 - Freescale/NXP i.MX31 Lite Development Kit
 - Buglabs i.MX31 Bug 1.x prototype
 - Arm Integrator/AP with CM1136JF-S core module

To my knowledge, none of these have any actual users aside from
reference boards being used to more easily test the platforms.

There are also a few ARM1136r1 machines, which implement the
ARMv6K SMP support (barriers, atomics and TLS):

 - Eukrea CPUIMX35 reference platform
 - Freescale/NXP i.MX35 Product Development Kit
 - ARM Integrator/CP/IM-LT3 with ARM1136J Core Tile
 - ARM Realview/EB with ARM1136J Core Tile

Again, these are mainly reference implementations rather than
actual products, but since they support ARMv6K, they should
continue to work correctly in SMP-enabled kernels. For the
ARM Core Tile, I have not found a datasheet but instead use
the revision based on what the respective virtual models
report.

All the other ARMv6 platforms use an ARM1176 with ARMv6K,
VMSAv7 and Trustzone support.

To avoid the broken configuration, annotate the ARM1136 based
machines with specific CPU_ARM1136R0 or CPU_ARM1136R2 symbols
in Kconfig and make the r0 variants depend on !SMP.

Link: https://lore.kernel.org/linux-arm-kernel/2831c5a6-cfbf-4fe0-b51c-0396e5b0aeb7@app.fastmail.com/T/
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Aaro Koskinen <aaro.koskinen@iki.fi> # OMAP
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

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