x86/irq: Add and use NR_EXTERNAL_VECTORS and NR_SYSTEM_VECTORS

Add defines for the number of external vectors and number of system
vectors instead of requiring the use of (FIRST_SYSTEM_VECTOR -
FIRST_EXTERNAL_VECTOR) and (NR_VECTORS - FIRST_SYSTEM_VECTOR)
respectively. Clean up the usage sites.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lore.kernel.org/r/20210519212154.511983-3-hpa@zytor.com

Author: H. Peter Anvin (Intel)

arch/x86/include/asm/idtentry.h

@@ -504,7 +504,7 @@ __visible noinstr void func(struct pt_regs *regs,			\
 	.align 8
 SYM_CODE_START(irq_entries_start)
     vector=FIRST_EXTERNAL_VECTOR
-    .rept (FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
+    .rept NR_EXTERNAL_VECTORS
 	UNWIND_HINT_IRET_REGS
 0 :
 	.byte	0x6a, vector
@@ -520,7 +520,7 @@ SYM_CODE_END(irq_entries_start)
 	.align 8
 SYM_CODE_START(spurious_entries_start)
     vector=FIRST_SYSTEM_VECTOR
-    .rept (NR_VECTORS - FIRST_SYSTEM_VECTOR)
+    .rept NR_SYSTEM_VECTORS
 	UNWIND_HINT_IRET_REGS
 0 :
 	.byte	0x6a, vector

arch/x86/include/asm/irq_vectors.h

@@ -114,6 +114,9 @@
 #define FIRST_SYSTEM_VECTOR		NR_VECTORS
 #endif
 
+#define NR_EXTERNAL_VECTORS		(FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
+#define NR_SYSTEM_VECTORS		(NR_VECTORS - FIRST_SYSTEM_VECTOR)
+
 /*
  * Size the maximum number of interrupts.
  *

tools/arch/x86/include/asm/irq_vectors.h

@@ -114,6 +114,9 @@
 #define FIRST_SYSTEM_VECTOR		NR_VECTORS
 #endif
 
+#define NR_EXTERNAL_VECTORS		(FIRST_SYSTEM_VECTOR - FIRST_EXTERNAL_VECTOR)
+#define NR_SYSTEM_VECTORS		(NR_VECTORS - FIRST_SYSTEM_VECTOR)
+
 /*
  * Size the maximum number of interrupts.
  *