xtensa: fix cache aliasing handling code for WT cache

Currently building kernel for xtensa core with aliasing WT cache fails
with the following messages:

  mm/memory.c:2152: undefined reference to `flush_dcache_page'
  mm/memory.c:2332: undefined reference to `local_flush_cache_page'
  mm/memory.c:1919: undefined reference to `local_flush_cache_range'
  mm/memory.c:4179: undefined reference to `copy_to_user_page'
  mm/memory.c:4183: undefined reference to `copy_from_user_page'

This happens because implementation of these functions is only compiled
when data cache is WB, which looks wrong: even when data cache doesn't
need flushing it still needs invalidation. The functions like
__flush_[invalidate_]dcache_* are correctly defined for both WB and WT
caches (and even if they weren't that'd still be ok, just slower).

Fix this by providing the same implementation of the above functions for
both WB and WT cache.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

arch/xtensa/mm/cache.c

@@ -120,10 +120,6 @@ void copy_user_highpage(struct page *dst, struct page *src,
 	preempt_enable();
 }
 
-#endif /* DCACHE_WAY_SIZE > PAGE_SIZE */
-
-#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
-
 /*
  * Any time the kernel writes to a user page cache page, or it is about to
  * read from a page cache page this routine is called.
@@ -208,7 +204,7 @@ void local_flush_cache_page(struct vm_area_struct *vma, unsigned long address,
 	__invalidate_icache_page_alias(virt, phys);
 }
 
-#endif
+#endif /* DCACHE_WAY_SIZE > PAGE_SIZE */
 
 void
 update_mmu_cache(struct vm_area_struct * vma, unsigned long addr, pte_t *ptep)
@@ -225,7 +221,7 @@ update_mmu_cache(struct vm_area_struct * vma, unsigned long addr, pte_t *ptep)
 
 	flush_tlb_page(vma, addr);
 
-#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
+#if (DCACHE_WAY_SIZE > PAGE_SIZE)
 
 	if (!PageReserved(page) && test_bit(PG_arch_1, &page->flags)) {
 		unsigned long phys = page_to_phys(page);
@@ -256,7 +252,7 @@ update_mmu_cache(struct vm_area_struct * vma, unsigned long addr, pte_t *ptep)
  * flush_dcache_page() on the page.
  */
 
-#if (DCACHE_WAY_SIZE > PAGE_SIZE) && XCHAL_DCACHE_IS_WRITEBACK
+#if (DCACHE_WAY_SIZE > PAGE_SIZE)
 
 void copy_to_user_page(struct vm_area_struct *vma, struct page *page,
 		unsigned long vaddr, void *dst, const void *src,