riscv: Add scalar crypto extensions support

When the scalar extensions are available expose them to the guest
via device tree so that guest can use it. This includes extensions
Zbkb, Zbkc, Zbkx, Zknd, Zkne, Zknh, Zkr, Zksed, Zksh, and Zkt.

The Zkr extension requires SEED CSR emulation in user space so
we also add related KVM_EXIT_RISCV_CSR handling.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20240325153141.6816-5-apatel@ventanamicro.com


Signed-off-by: Will Deacon <will@kernel.org>