hw/pci-host/astro: Implement Hard Fail and Soft Fail mode

hw/pci-host/astro: Implement Hard Fail and Soft Fail mode

The Astro/Elroy chip can work in either Hard-Fail or Soft-Fail mode.

Hard fail means the system bus will send an HPMC (=crash) to the
processor, soft fail means the system bus will ignore timeouts of
MMIO-reads or MMIO-writes and return -1ULL.

The HF mode is controlled by a bit in the status register and is usually
programmed by the OS. Return the corresponing values based on the current
value of that bit.

Signed-off-by: Helge Deller <deller@gmx.de>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>