treewide: remove redundant #include <linux/kconfig.h>

Kernel source files need not include <linux/kconfig.h> explicitly
because the top Makefile forces to include it with:

  -include $(srctree)/include/linux/kconfig.h

This commit removes explicit includes except the following:

  * arch/s390/include/asm/facilities_src.h
  * tools/testing/radix-tree/linux/kernel.h

These two are used for host programs.

Link: http://lkml.kernel.org/r/1473656164-11929-1-git-send-email-yamada.masahiro@socionext.com
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/usb/early/ehci-dbgp.c

@@ -20,7 +20,6 @@
 #include <linux/usb/ehci_def.h>
 #include <linux/delay.h>
 #include <linux/serial_core.h>
-#include <linux/kconfig.h>
 #include <linux/kgdb.h>
 #include <linux/kthread.h>
 #include <asm/io.h>

drivers/usb/gadget/udc/bcm63xx_udc.c

@@ -21,7 +21,6 @@
 #include <linux/errno.h>
 #include <linux/interrupt.h>
 #include <linux/ioport.h>
-#include <linux/kconfig.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/module.h>

drivers/usb/host/pci-quirks.c

@@ -9,7 +9,6 @@
  */
 
 #include <linux/types.h>
-#include <linux/kconfig.h>
 #include <linux/kernel.h>
 #include <linux/pci.h>
 #include <linux/delay.h>