x86/ioapic: add prototype for io_apic_gsi_base to io_apic.h

So that the function can be called from other files without adding prototypes
to each of them.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>

xen/arch/x86/io_apic.c

@@ -2274,8 +2274,6 @@ static int ioapic_physbase_to_id(unsigned long physbase)
     return -EINVAL;
 }
 
-unsigned apic_gsi_base(int apic);
-
 static int apic_pin_2_gsi_irq(int apic, int pin)
 {
     int idx;
@@ -2286,7 +2284,7 @@ static int apic_pin_2_gsi_irq(int apic, int pin)
     idx = find_irq_entry(apic, pin, mp_INT);
 
     return idx >= 0 ? pin_2_irq(idx, apic, pin)
-                    : apic_gsi_base(apic) + pin;
+                    : io_apic_gsi_base(apic) + pin;
 }
 
 int ioapic_guest_read(unsigned long physbase, unsigned int reg, u32 *pval)

xen/arch/x86/mpparse.c

@@ -913,7 +913,7 @@ unsigned __init highest_gsi(void)
 	return res;
 }
 
-unsigned apic_gsi_base(int apic)
+unsigned int io_apic_gsi_base(unsigned int apic)
 {
 	return mp_ioapic_routing[apic].gsi_base;
 }

xen/include/asm-x86/io_apic.h

@@ -127,6 +127,9 @@ struct __packed IO_APIC_route_entry {
 /* I/O APIC entries */
 extern struct mpc_config_ioapic mp_ioapics[MAX_IO_APICS];
 
+/* Base GSI for this IO APIC */
+unsigned int io_apic_gsi_base(unsigned int apic);
+
 /* Only need to remap ioapic RTE (reg: 10~3Fh) */
 #define ioapic_reg_remapped(reg) (iommu_intremap && ((reg) >= 0x10))