[IA64] Set default page size to 64k

It seems that 16k page size causes Itanium processors to have significant
TLB overhead when the working set is growing beyond 2M. Setting the
page size to 64k reduces this problem.

See the paper of the researchers at the TU Dresden on TLB issues:
http://www.cs.utah.edu/wmpi/2006/final-version/wmpi-posters-3-Juckeland.pdf
and my presentation
http://ftp.kernel.org/pub/linux/kernel/people/christoph/gelato/gelato2007-tlb-tricks.pdf.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6.21-rc7-mm1/arch/ia64/Kconfig
===================================================================
--- linux-2.6.21-rc7-mm1.orig/arch/ia64/Kconfig	2007-04-25 09:48:22.000000000 -0700
+++ linux-2.6.21-rc7-mm1/arch/ia64/Kconfig	2007-04-25 09:48:57.000000000 -0700
@@ -168,7 +168,7 @@ endchoice
 
 choice
 	prompt "Kernel page size"
-	default IA64_PAGE_SIZE_16KB
+	default IA64_PAGE_SIZE_64KB
 
 config IA64_PAGE_SIZE_4KB
 	bool "4KB"