arch-arm: Reimplement TLB::flushAll

arch-arm: Reimplement TLB::flushAll

flushAll is a non architectural flush command; this is not based on
flushAllSecurity anymore. flushAll should always flush stage1 and stage2,
whereas flushAllSecurity is checking for the current state
(vmid, and if we are in Hyp)

Change-Id: I6b81ebfba387e646f256ecbecb7b5ee720745358
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/35239
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Richard Cooper <richard.cooper@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>