hw/arm/sbsa-ref: use XHCI to replace EHCI

The current sbsa-ref cannot use EHCI controller which is only
able to do 32-bit DMA, since sbsa-ref doesn't have RAM below 4GB.
Hence, this uses XHCI to provide a usb controller with 64-bit
DMA capablity instead of EHCI.

We bump the platform version to 0.3 with this change.  Although the
hardware at the USB controller address changes, the firmware and
Linux can both cope with this -- on an older non-XHCI-aware
firmware/kernel setup the probe routine simply fails and the guest
proceeds without any USB.  (This isn't a loss of functionality,
because the old USB controller never worked in the first place.) So
we can call this a backwards-compatible change and only bump the
minor version.

Signed-off-by: Yuquan Wang <wangyuquan1236@phytium.com.cn>
Message-id: 20230621103847.447508-2-wangyuquan1236@phytium.com.cn
[PMM: tweaked commit message; add line to docs about what
 changes in platform version 0.3]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>