RISC-V: KVM: Add common nested acceleration support

Add a common nested acceleration support which will be shared by
all parts of KVM RISC-V. This nested acceleration support detects
and enables SBI NACL extension usage based on static keys which
ensures minimum impact on the non-nested scenario.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20241020194734.58686-9-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>

arch/riscv/kvm/Makefile

@@ -16,6 +16,7 @@ kvm-y += aia_device.o
 kvm-y += aia_imsic.o
 kvm-y += main.o
 kvm-y += mmu.o
+kvm-y += nacl.o
 kvm-y += tlb.o
 kvm-y += vcpu.o
 kvm-y += vcpu_exit.o