[ARM] 5545/2: add flush_kernel_dcache_page() for ARM

Without this, the default implementation is a no op which is completely
wrong with a VIVT cache, and usage of sg_copy_buffer() produces
unpredictable results.

Tested-by: Sebastian Andrzej Siewior <bigeasy@breakpoint.cc>

CC: stable@kernel.org
Signed-off-by: Nicolas Pitre <nico@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

arch/arm/include/asm/cacheflush.h

@@ -429,6 +429,14 @@ static inline void flush_anon_page(struct vm_area_struct *vma,
 		__flush_anon_page(vma, page, vmaddr);
 }
 
+#define ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE
+static inline void flush_kernel_dcache_page(struct page *page)
+{
+	/* highmem pages are always flushed upon kunmap already */
+	if ((cache_is_vivt() || cache_is_vipt_aliasing()) && !PageHighMem(page))
+		__cpuc_flush_dcache_page(page_address(page));
+}
+
 #define flush_dcache_mmap_lock(mapping) \
 	spin_lock_irq(&(mapping)->tree_lock)
 #define flush_dcache_mmap_unlock(mapping) \