powerpc/64s: Rewrite __real_pte() and __rpte_to_hidx() as static inline

Rewrite __real_pte() and __rpte_to_hidx() as static inline in order to
avoid following warnings/errors when building with 4k page size:

	  CC      arch/powerpc/mm/book3s64/hash_tlb.o
	arch/powerpc/mm/book3s64/hash_tlb.c: In function 'hpte_need_flush':
	arch/powerpc/mm/book3s64/hash_tlb.c:49:16: error: variable 'offset' set but not used [-Werror=unused-but-set-variable]
	   49 |         int i, offset;
	      |                ^~~~~~

	  CC      arch/powerpc/mm/book3s64/hash_native.o
	arch/powerpc/mm/book3s64/hash_native.c: In function 'native_flush_hash_range':
	arch/powerpc/mm/book3s64/hash_native.c:782:29: error: variable 'index' set but not used [-Werror=unused-but-set-variable]
	  782 |         unsigned long hash, index, hidx, shift, slot;
	      |                             ^~~~~

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202501081741.AYFwybsq-lkp@intel.com/
Fixes: ff31e10 ("powerpc/mm/hash64: Store the slot information at the right offset for hugetlb")
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/e0d340a5b7bd478ecbf245d826e6ab2778b74e06.1736706263.git.christophe.leroy@csgroup.eu

Author: chleroy

arch/powerpc/include/asm/book3s/64/hash-4k.h

@@ -77,9 +77,17 @@
 /*
  * With 4K page size the real_pte machinery is all nops.
  */
-#define __real_pte(e, p, o)		((real_pte_t){(e)})
+static inline real_pte_t __real_pte(pte_t pte, pte_t *ptep, int offset)
+{
+	return (real_pte_t){pte};
+}
+
 #define __rpte_to_pte(r)	((r).pte)
-#define __rpte_to_hidx(r,index)	(pte_val(__rpte_to_pte(r)) >> H_PAGE_F_GIX_SHIFT)
+
+static inline unsigned long __rpte_to_hidx(real_pte_t rpte, unsigned long index)
+{
+	return pte_val(__rpte_to_pte(rpte)) >> H_PAGE_F_GIX_SHIFT;
+}
 
 #define pte_iterate_hashed_subpages(rpte, psize, va, index, shift)       \
 	do {							         \