KVM: x86: Drop MAX_NR_RESERVED_IOAPIC_PINS, use KVM_MAX_IRQ_ROUTES directly

Directly use KVM_MAX_IRQ_ROUTES when checking the number of routes being
defined by userspace when creating a split IRQCHIP.  The restriction has
nothing to do with the I/O APIC, e.g. most modern userspace usage is for
routing MSIs.  Breaking the unnecessary dependency on the I/O APIC will
allow burying all of ioapic.h behind CONFIG_KVM_IOAPIC=y.

No functional change intended.

Link: https://patch.msgid.link/20251206004311.479939-6-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/kvm/ioapic.h

@@ -10,7 +10,6 @@ struct kvm;
 struct kvm_vcpu;
 
 #define IOAPIC_NUM_PINS  KVM_IOAPIC_NUM_PINS
-#define MAX_NR_RESERVED_IOAPIC_PINS KVM_MAX_IRQ_ROUTES
 #define IOAPIC_VERSION_ID 0x11	/* IOAPIC version */
 #define IOAPIC_EDGE_TRIG  0
 #define IOAPIC_LEVEL_TRIG 1

arch/x86/kvm/x86.c

@@ -6717,7 +6717,7 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
 	case KVM_CAP_SPLIT_IRQCHIP: {
 		mutex_lock(&kvm->lock);
 		r = -EINVAL;
-		if (cap->args[0] > MAX_NR_RESERVED_IOAPIC_PINS)
+		if (cap->args[0] > KVM_MAX_IRQ_ROUTES)
 			goto split_irqchip_unlock;
 		r = -EEXIST;
 		if (irqchip_in_kernel(kvm))