Patch for modularising ioapic.[c/h] and related files.

This adds few functions to access the daata structures
defined inside ioapic.c. Removes the same data structures
from ioapic.h
Also this modifies some of the names of existing APIs to
conform to the ioapic module name.
Modified gsi_table identifier to gs_table_data, to avoid
a MISRA C Violation.

Tracked-On: #1842
Signed-off-by: Arindam Roy <arindam.roy@intel.com>

hypervisor/debug/vuart.c

@@ -29,6 +29,7 @@
  */
 
 #include <hypervisor.h>
+#include <ioapic.h>
 
 #include "uart16550.h"