riscv: do not select non-existing config ANON_INODES

Commit 99cdc6c1 ("RISC-V: Add initial skeletal KVM support") selects
the config ANON_INODES in config KVM, but the config ANON_INODES is removed
since commit 5dd50aae

 ("Make anon_inodes unconditional") in 2018.

Hence, ./scripts/checkkconfigsymbols.py warns on non-existing symbols:

  ANON_INODES
  Referencing files: arch/riscv/kvm/Kconfig

Remove selecting the non-existing config ANON_INODES.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Message-Id: <20211022061514.25946-1-lukas.bulwahn@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>