genirq: Drop 5 #included header files from irq.h

<linux/irq.h> does not use nor need several of its #included files,
so drop those header files from irq.h.

<linux/irq.h> is currently #included in around 1135 C source files
(oops, I didn't count other header files that #include it), making it
the 29th most-used header file.

Build tested on i386 and x86_64 * (allnoconfig, tiny.config, defconfig,
allyesconfig, and allmodconfig) and x64_64 allmodconfig + SMP=disabled.
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/02745e91-c117-74b5-d043-dceb3d4bb4e0@infradead.org

include/linux/irq.h

@@ -10,18 +10,13 @@
  * Thanks. --rmk
  */
 
-#include <linux/smp.h>
-#include <linux/linkage.h>
 #include <linux/cache.h>
 #include <linux/spinlock.h>
 #include <linux/cpumask.h>
-#include <linux/gfp.h>
 #include <linux/irqhandler.h>
 #include <linux/irqreturn.h>
 #include <linux/irqnr.h>
-#include <linux/errno.h>
 #include <linux/topology.h>
-#include <linux/wait.h>
 #include <linux/io.h>
 #include <linux/slab.h>