hv: validate input for dmar_free_irte function

 Malicious input 'index' may trigger buffer
 overflow on array 'irte_alloc_bitmap[]'.

 This patch validate that 'index' shall be
 less than 'CONFIG_MAX_IR_ENTRIES' and also
 remove unnecessary check on 'index' in
 'ptirq_free_irte()' function with this fix.

Tracked-On: #6132
Signed-off-by: Yonghua Huang <yonghua.huang@intel.com>