Trusted Firmware stopped booting on SBSA-ref

Since commit 48da29e4 ("target/arm: Add ptw_idx to S1Translate"), TF-A doesn't boot anymore on the SBSA-ref machine.

Expected result:

./qemu-system-aarch64 -display none -machine sbsa-ref -serial mon:stdio -cpu cortex-a57 \
  -drive if=pflash,file=SBSA_FLASH0.fd,format=raw,snapshot=on \
  -drive if=pflash,file=SBSA_FLASH1.fd,format=raw,snapshot=on 
NOTICE:  Booting Trusted Firmware
NOTICE:  BL1: v2.5(release):v2.5-432-ga4ea20502
NOTICE:  BL1: Built : 13:50:23, Sep 13 2021
NOTICE:  BL1: Booting BL2
NOTICE:  BL2: v2.5(release):v2.5-432-ga4ea20502
NOTICE:  BL2: Built : 13:50:23, Sep 13 2021
NOTICE:  BL1: Booting BL31
NOTICE:  BL31: v2.5(release):v2.5-432-ga4ea20502
NOTICE:  BL31: Built : 13:50:23, Sep 13 2021
QEMU 7.1.50 monitor - type 'help' for more information
(qemu) q

SBSA_FLASH0.fd.xz SBSA_FLASH1.fd.xz