[IA64] move defconfig to arch/ia64/configs/

This patch moves the default ia64 defconfig to
arch/ia64/configs/generic_defconfig where it belongs and selects it as
the default defconfig through KBUILD_DEFCONFIG.
Signed-off-by: Adrian Bunk <adrian.bunk@movial.fi>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/Makefile

@@ -11,6 +11,8 @@
 # Copyright (C) 1998-2004 by David Mosberger-Tang <davidm@hpl.hp.com>
 #
 
+KBUILD_DEFCONFIG := generic_defconfig
+
 NM := $(CROSS_COMPILE)nm -B
 READELF := $(CROSS_COMPILE)readelf