arm/arm-powerctl: set NSACR.{CP11, CP10} bits in arm_set_cpu_on()

arm/arm-powerctl: set NSACR.{CP11, CP10} bits in arm_set_cpu_on()

This change ensures that the FPU can be accessed in Non-Secure mode
when the CPU core is reset using the arm_set_cpu_on() function call.
The NSACR.{CP11,CP10} bits define the exception level required to
access the FPU in Non-Secure mode. Without these bits set, the CPU
will give an undefined exception trap on the first FPU access for the
secondary cores under Linux.

This is necessary because in this power-control codepath QEMU
is effectively emulating a bit of EL3 firmware, and has to set
the CPU up as the EL3 firmware would.

Fixes: fc1120a7f5
Cc: qemu-stable@nongnu.org
Signed-off-by: Niek Linnenbank <nieklinnenbank@gmail.com>
[PMM: added clarifying para to commit message]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>