riscv: Add Svinval extension support

Svinval extension allows the guest OS to perform range based TLB
maintenance efficiently. Add the Svinval extensiont to the device
tree if it is supported by the host.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Link: https://lore.kernel.org/r/20221018140854.69846-3-apatel@ventanamicro.com


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