RISC-V: KVM: Use nacl_csr_xyz() for accessing H-extension CSRs

RISC-V: KVM: Use nacl_csr_xyz() for accessing H-extension CSRs

When running under some other hypervisor, prefer nacl_csr_xyz()
for accessing H-extension CSRs in the run-loop. This makes CSR
access faster whenever SBI nested acceleration is available.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Link: https://lore.kernel.org/r/20241020194734.58686-10-apatel@ventanamicro.com
Signed-off-by: Anup Patel <anup@brainfault.org>