hw/arm/collie: Put StrongARMState* into a CollieMachineState struct

hw/arm/collie: Put StrongARMState* into a CollieMachineState struct

Coverity complains that the collie_init() function leaks the memory
allocated in sa1110_init().  This is true but not significant since
the function is called only once on machine init and the memory must
remain in existence until QEMU exits anyway.

Still, we can avoid the technical memory leak by keeping the pointer
to the StrongARMState inside the machine state struct.  Switch from
the simple DEFINE_MACHINE() style to defining a subclass of
TYPE_MACHINE which extends the MachineState struct, and keep the
pointer there.

Fixes: CID 1421921
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20200326204919.22006-1-peter.maydell@linaro.org