idle: i7300: add PCI dependency

BugLink: http://bugs.launchpad.net/bugs/1756866

GCC correctly points out an uninitialized variable use when CONFIG_PCI is disabled.

drivers/idle/i7300_idle.c: In function 'i7300_idle_notifier':
include/asm-generic/bug.h:119:5: error: 'got_ctl' may be used uninitialized in this function [-Werror=maybe-uninitialized]
  if (unlikely(__ret_warn_once && !__warned)) {  \
     ^
drivers/idle/i7300_idle.c:415:5: note: 'got_ctl' was declared here
  u8 got_ctl;
     ^~~~~~~

The driver no longer exists in later kernels, so this patch only appplies to
linux-4.9.y and earlier.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

drivers/idle/Kconfig

@@ -17,6 +17,7 @@ config I7300_IDLE_IOAT_CHANNEL
 
 config I7300_IDLE
 	tristate "Intel chipset idle memory power saving driver"
+	depends on PCI
 	select I7300_IDLE_IOAT_CHANNEL
 	help
 	  Enable memory power savings when idle with certain Intel server