Don't bother unprotecting the target gfn if EMULTYPE_WRITE_PF_TO_SP is
set, as KVM will simply report the emulation failure to userspace.  This
will allow converting reexecute_instruction() to use
kvm_mmu_unprotect_gfn_instead_retry() instead of kvm_mmu_unprotect_page().

Link: https://lore.kernel.org/r/20240831001538.336683-17-seanjc@google.comSigned-off-by: Sean Christopherson <seanjc@google.com>