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 <[email protected]>
Message-ID: <[email protected]>
Reviewed-by: Alistair Francis <[email protected]>
Signed-off-by: Alistair Francis <[email protected]>

Author: danielhb