target/arm: Move arm_current_el() and arm_el_is_aa64() to internals.h

target/arm: Move arm_current_el() and arm_el_is_aa64() to internals.h

The functions arm_current_el() and arm_el_is_aa64() are used only in
target/arm and in hw/intc/arm_gicv3_cpuif.c.  They're functions that
query internal state of the CPU.  Move them out of cpu.h and into
internals.h.

This means we need to include internals.h in arm_gicv3_cpuif.c, but
this is justifiable because that file is implementing the GICv3 CPU
interface, which really is part of the CPU proper; we just ended up
implementing it in code in hw/intc/ for historical reasons.

The motivation for this move is that we'd like to change
arm_el_is_aa64() to add a condition that uses cpu_isar_feature();
but we don't want to include cpu-features.h in cpu.h.

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