arm64: avoid clang warning about self-assignment

Building a preprocessed source file for arm64 now always produces
a warning with clang because of the page_to_virt() macro assigning
a variable to itself.

Adding a new temporary variable avoids this issue.

Fixes: 2813b9c0 ("kasan, mm, arm64: tag non slab memory allocated via pagealloc")
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/include/asm/memory.h

@@ -316,8 +316,9 @@ static inline void *phys_to_virt(phys_addr_t x)
 #define page_to_virt(page)	({					\
 	unsigned long __addr =						\
 		((__page_to_voff(page)) | PAGE_OFFSET);			\
-	__addr = __tag_set(__addr, page_kasan_tag(page));		\
-	((void *)__addr);						\
+	unsigned long __addr_tag =					\
+		 __tag_set(__addr, page_kasan_tag(page));		\
+	((void *)__addr_tag);						\
 })
 
 #define virt_to_page(vaddr)	((struct page *)((__virt_to_pgoff(vaddr)) | VMEMMAP_START))