riscv: uaccess: fix type of 0 variable on error in get_user()

If the get_user(x, ptr) has x as a pointer, then the setting
of (x) = 0 is going to produce the following sparse warning,
so fix this by forcing the type of 'x' when access_ok() fails.

fs/aio.c:2073:21: warning: Using plain integer as NULL pointer
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Link: https://lore.kernel.org/r/20221229170545.718264-1-ben-linux@fluff.org
Cc: stable@vger.kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

arch/riscv/include/asm/uaccess.h

@@ -165,7 +165,7 @@ do {								\
 	might_fault();						\
 	access_ok(__p, sizeof(*__p)) ?		\
 		__get_user((x), __p) :				\
-		((x) = 0, -EFAULT);				\
+		((x) = (__force __typeof__(x))0, -EFAULT);	\
 })
 
 #define __put_user_asm(insn, x, ptr, err)			\