roms/opensbi: Update to v1.5.1

roms/opensbi: Update to v1.5.1

A new minor version of OpenSBI was just released after our bump to
OpenSBI 1.5. It contains significant bug fixes that it's worth doing
a new update for QEMU 9.1.

Submodule roms/opensbi 455de672dd..43cace6c36:
  > lib: sbi: check result of pmp_get() in is_pmp_entry_mapped()
  > lib: sbi: fwft: fix incorrect size passed to sbi_zalloc()
  > lib: sbi: dbtr: fix potential NULL pointer dereferences
  > include: Adjust Sscofpmf mhpmevent mask for upper 8 bits
  > lib: sbi_hsm: Save/restore menvcfg only when it exists

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20240805120259.1705016-2-dbarboza@ventanamicro.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>