arm64: mm: Really fix sparse warning in untagged_addr()

untagged_addr() can be called with a '__user' pointer parameter and must
therefore use '__force' casts both when passing this parameter through
to sign_extend64() as a 'u64', but also when casting the 's64' return
value back to the '__user' pointer type.
Signed-off-by: Will Deacon <will@kernel.org>

arch/arm64/include/asm/memory.h

@@ -201,7 +201,7 @@ extern u64			vabits_user;
  * pass on to access_ok(), for instance.
  */
 #define untagged_addr(addr)	\
-	((__typeof__(addr))sign_extend64((__force u64)(addr), 55))
+	((__force __typeof__(addr))sign_extend64((__force u64)(addr), 55))
 
 #ifdef CONFIG_KASAN_SW_TAGS
 #define __tag_shifted(tag)	((u64)(tag) << 56)