ia64: old_rr4 added under CONFIG_HUGETLB_PAGE

kernel test robot throws below warning ->

arch/ia64/include/asm/mmu_context.h: In function 'reload_context':
   arch/ia64/include/asm/mmu_context.h:127:48: warning: variable
'old_rr4' set but not used [-Wunused-but-set-variable]
     127 |         unsigned long rr0, rr1, rr2, rr3, rr4, old_rr4;

Add it under CONFIG_HUGETLB_PAGE

Link: https://lkml.kernel.org/r/20220626022114.4020-1-jrdr.linux@gmail.comSigned-off-by: Souptick Joarder (HPE) <jrdr.linux@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/ia64/include/asm/mmu_context.h

@@ -124,9 +124,12 @@ reload_context (nv_mm_context_t context)
 {
 	unsigned long rid;
 	unsigned long rid_incr = 0;
-	unsigned long rr0, rr1, rr2, rr3, rr4, old_rr4;
+	unsigned long rr0, rr1, rr2, rr3, rr4;
 
+#ifdef CONFIG_HUGETLB_PAGE
+	unsigned long old_rr4;
 	old_rr4 = ia64_get_rr(RGN_BASE(RGN_HPAGE));
+#endif
 	rid = context << 3;	/* make space for encoding the region number */
 	rid_incr = 1 << 8;