roms/opensbi: Update to v1.8.1

Update OpenSBI and the pre-built opensbi32 and opensbi64 images to version 1.8.1. We're going for the intermediate/bug fix release 1.8.1 directly due to a PMP related fix that was impacting QEMU profile CPUs. Changelog for v1.8.1: * Typo fix in comments of sbi_hartindex_to_hartid() * Fix hart protection abstraction for platforms without PMP Changelog for v1.8 includes, among other things: - IPI device ratings - SiFive CLINT v2 support - SiFive PL2 cache controller driver - SiFive Extensible Cache (EC) driver - SiFive TMC0 based HSM driver - SiFive SMC0 based system suspend driver - MPXY RPMI mailbox driver for voltage service group - MPXY RPMI mailbox driver for device power service group - MPXY RPMI mailbox driver for performance service group Check out the full release log at [1] for more info. [1] https://github.com/riscv-software-src/opensbi/releases/tag/v1.8 Signed-off-by: Daniel Henrique Barboza <daniel.barboza@oss.qualcomm.com> Reviewed-by: Alistair Francis <alistair.francis@wdc.com> Message-ID: <20260108160825.171794-1-daniel.barboza@oss.qualcomm.com> Signed-off-by: Alistair Francis <alistair.francis@wdc.com>