ANDROID: x86: pkvm: Use kvm_hypercall4 to send hypercalls to the pkvm host

Currently there are two hypercalls PKVM_GHC_IOWRITE and PKVM_GHC_IOREAD
need to be emulated by the pkvm host. The RAX/RBX/RCX/RDX/RSI will be
shared with the pkvm host for emulation by the pkvm hypervisor. Use
kvm_hypercall4 for these hypercalls to make sure no valuable information
stored in these 5 registers.

Bug: 351790050
Upstream-Task: 402758258

Fixes: 741de0b8 ("ANDROID: pkvm: vmx: Share pVM vcpu state to the host for handling vmcall")
Change-Id: Ia49e70bf9cc66a9a458a350e760b10c8c520dfce
Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>