init_task: Replace CONFIG_HAVE_GENERIC_INIT_TASK

Now that all archs except ia64 are converted, replace the config and
let the ia64 select CONFIG_ARCH_INIT_TASK

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20120503085035.867948914@linutronix.de

diff --git a/arch/ia64/Kconfig b/arch/ia64/Kconfig
index 1197547..022ea3a 100644
--- a/arch/ia64/Kconfig
+++ b/arch/ia64/Kconfig
@@ -34,6 +34,7 @@
 	select ARCH_HAVE_NMI_SAFE_CMPXCHG
 	select GENERIC_IOMAP
 	select GENERIC_SMP_IDLE_THREAD
+	select ARCH_INIT_TASK
 	default y
 	help
 	  The Itanium Processor Family is Intel's 64-bit successor to