target/arm: Move id_pfr0, id_pfr1 into ARMISARegisters

Move the id_pfr0 and id_pfr1 fields into the ARMISARegisters
sub-struct. We're going to want id_pfr1 for an isar_features
check, and moving both at the same time avoids an odd
inconsistency.

Changes other than the ones to cpu.h and kvm64.c made
automatically with:
  perl -p -i -e 's/cpu->id_pfr/cpu->isar.id_pfr/' target/arm/*.c hw/intc/armv7m_nvic.c

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20200910173855.4068-3-peter.maydell@linaro.org