roms/opensbi: Update to v1.7

roms/opensbi: Update to v1.7

Update OpenSBI and the pre-built opensbi32 and opensbi64 images to
version 1.7.

It has been almost an year since we last updated OpenSBI (at the time,
up to v1.5.1) and we're missing a lot of good stuff from both v1.6 and
v1.7, including SBI 3.0 and RPMI 1.0.

The changelog is too large and tedious to post in the commit msg so I
encourage refering to [1] and [2] to see the new features we're adding
into the QEMU roms.

[1] https://github.com/riscv-software-src/opensbi/releases/tag/v1.6
[2] https://github.com/riscv-software-src/opensbi/releases/tag/v1.7

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