KVM: x86: Drop superfluous kvm_hv_set_sint() => kvm_hv_synic_set_irq() wrapper

KVM: x86: Drop superfluous kvm_hv_set_sint() => kvm_hv_synic_set_irq() wrapper

Drop the superfluous kvm_hv_set_sint() and instead wire up ->set() directly
to its final destination, kvm_hv_synic_set_irq().  Keep hv_synic_set_irq()
instead of kvm_hv_set_sint() to provide some amount of consistency in the
->set() helpers, e.g. to match kvm_pic_set_irq() and kvm_ioapic_set_irq().

kvm_set_msi() is arguably the oddball, e.g. kvm_set_msi_irq() should be
something like kvm_msi_to_lapic_irq() so that kvm_set_msi() can instead be
kvm_set_msi_irq(), but that's a future problem to solve.

No functional change intended.

Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Kai Huang <kai.huang@intel.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Acked-by: Kai Huang <kai.huang@intel.com>
Link: https://lore.kernel.org/r/20250611213557.294358-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>