hw/boards: Do not create unusable default if=sd drives

hw/boards: Do not create unusable default if=sd drives

A number of machines create an if=sd drive by default even though
they lack an SD bus, and therefore cannot use the drive.

This drive is created when the machine sets flag
@auto_create_sdcard.

See for example running HMP "info block" on the HPPA C3700 machine:

  $ qemu-system-hppa -M C3700 -monitor stdio -S
  (qemu) info block

  floppy0: [not inserted]
      Removable device: not locked, tray closed

  sd0: [not inserted]
      Removable device: not locked, tray closed

  $ qemu-system-hppa -M C3700 -sd /bin/sh
  qemu-system-hppa: -sd /bin/sh: machine type does not support if=sd,bus=0,unit=0

Delete that from machines that lack an SD bus.

Note, only the ARM and RISCV targets use such feature:

 $ git grep -wl IF_SD hw | cut -d/ -f-2 | sort -u
 hw/arm
 hw/riscv
 $

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20250204200934.65279-5-philmd@linaro.org>