x86/vector: Remove the unused macro FPU_IRQ

The macro FPU_IRQ has never been used since v3.10, So remove it.
Signed-off-by: Dou Liyang <douly.fnst@cn.fujitsu.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: hpa@zytor.com
Link: https://lkml.kernel.org/r/20180426060832.27312-1-douly.fnst@cn.fujitsu.com

arch/x86/include/asm/irq_vectors.h

@@ -114,8 +114,6 @@
 #define FIRST_SYSTEM_VECTOR		NR_VECTORS
 #endif
 
-#define FPU_IRQ				  13
-
 /*
  * Size the maximum number of interrupts.
  *