KVM: x86: Have ____kvm_emulate_hypercall() read the GPRs

KVM: x86: Have ____kvm_emulate_hypercall() read the GPRs

Have ____kvm_emulate_hypercall() read the GPRs instead of passing them
in via the macro.

When emulating KVM hypercalls via TDVMCALL, TDX will marshall registers of
TDVMCALL ABI into KVM's x86 registers to match the definition of KVM
hypercall ABI _before_ ____kvm_emulate_hypercall() gets called.  Therefore,
____kvm_emulate_hypercall() can just read registers internally based on KVM
hypercall ABI, and those registers can be removed from the
__kvm_emulate_hypercall() macro.

Also, op_64_bit can be determined inside ____kvm_emulate_hypercall(),
remove it from the __kvm_emulate_hypercall() macro as well.

No functional change intended.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Message-ID: <20250222014225.897298-2-binbin.wu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>