In the next commit we'll refactor the PIIX4 code out of
mips_malta_init(). As a preliminary step, add the 'ide_drives'
variable and create the drive array dynamically.
Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Reviewed-by: Li Qiang <liq3ea@gmail.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>