target/arm/arm-powerctl: Add new arm_set_cpu_on_and_reset()

target/arm/arm-powerctl: Add new arm_set_cpu_on_and_reset()

Currently the Arm arm-powerctl.h APIs allow:
 * arm_set_cpu_on(), which powers on a CPU and sets its
   initial PC and other startup state
 * arm_reset_cpu(), which resets a CPU which is already on
   (and fails if the CPU is powered off)

but there is no way to say "power on a CPU as if it had
just come out of reset and don't do anything else to it".

Add a new function arm_set_cpu_on_and_reset(), which does this.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20190219125808.25174-5-peter.maydell@linaro.org