[IA64] Use bitmaps for efficient context allocation/free

Corrects the very inefficent method of finding free context_ids in
get_mmu_context().  Instead of walking the task_list of all processes,
2 bitmaps are used to efficently store and lookup state, inuse and
needs flushing. The entire rid address space is now used before calling
wrap_mmu_context and global tlb flushing.

Special thanks to Ken and Rohit for their review and modifications in
using a bit flushmap.

Signed-off-by: Peter Keilty <peter.keilty@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>
diff --git a/arch/ia64/kernel/setup.c b/arch/ia64/kernel/setup.c
index fc56ca2..c9388a9 100644
--- a/arch/ia64/kernel/setup.c
+++ b/arch/ia64/kernel/setup.c
@@ -454,6 +454,7 @@
 #endif
 
 	cpu_init();	/* initialize the bootstrap CPU */
+	mmu_context_init();	/* initialize context_id bitmap */
 
 #ifdef CONFIG_ACPI
 	acpi_boot_init();