RISC-V: KVM: Prevent HGATP_MODE_BARE passed

RISC-V: KVM: Prevent HGATP_MODE_BARE passed

Current kvm_riscv_gstage_mode_detect() assumes H-extension must
have HGATP_MODE_SV39X4/SV32X4 at least, but the spec allows
H-extension with HGATP_MODE_BARE alone. The KVM depends on
!HGATP_MODE_BARE at least, so enhance the gstage-mode-detect
to block HGATP_MODE_BARE.

Move gstage-mode-check closer to gstage-mode-detect to prevent
unnecessary init.

Reviewed-by: Troy Mitchell <troy.mitchell@linux.dev>
Reviewed-by: Nutty Liu <nutty.liu@hotmail.com>
Signed-off-by: Guo Ren (Alibaba DAMO Academy) <guoren@kernel.org>
Reviewed-by: Fangyu Yu <fangyu.yu@linux.alibaba.com>
Link: https://lore.kernel.org/r/20250821142542.2472079-4-guoren@kernel.org
Signed-off-by: Anup Patel <anup@brainfault.org>