RISC-V: KVM: Remove redundant includes of asm/csr.h

We should include asm/csr.h only where required so let us remove
redundant includes of this header.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Anup Patel <anup@brainfault.org>