OpenSBI v1.5.1 Released

[Anup Patel]

Hi All,

The OpenSBI v1.5.1 is now available on GitHub at:
https://github.com/riscv-software-src/opensbi/releases

This intermediate release has following fixes:

* Save/restore menvcfg only when it exists
* Adjust Sscofpmf mhpmevent mask for upper 8 bits
* Fix potential NULL pointer dereferences in SBI DBTR
* Fix incorrect size passed to sbi_zalloc() in SBI FWFT
* Check result of pmp_get() in is_pmp_entry_mapped()

Many thanks to everyone who has contributed to this release.

Best Regards,
Anup Patel