target/arm: Advertise FEAT_ETS for '-cpu max'

The architectural feature FEAT_ETS (Enhanced Translation
Synchronization) is a set of tightened guarantees about memory
ordering involving translation table walks:

 * if memory access RW1 is ordered-before memory access RW2 then it
   is also ordered-before any translation table walk generated by RW2
   that generates a translation fault, address size fault or access
   fault

 * TLB maintenance on non-exec-permission translations is guaranteed
   complete after a DSB (ie it does not need the context
   synchronization event that you have to have if you don’t have
   FEAT_ETS)

For QEMU’s implementation we don’t reorder translation table walk
accesses, and we guarantee to finish the TLB maintenance as soon as
the TLB op is done (the tlb_flush functions will complete at the end
of the TLB, and TLB ops always end the TB because they’re sysreg
writes).

So we’re already compliant and all we need to do is say so in the ID
registers for the 'max' CPU.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20220819110052.2942289-6-peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>