sh: checksum: add missing linux/uaccess.h include

SuperH does not include uaccess.h, even tho it calls access_ok().

Fixes: 68f4eae7 ("net: checksum: drop the linux/uaccess.h include")
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Tested-by: Simon Horman <simon.horman@corigine.com>
Link: https://lore.kernel.org/r/20230128073108.1603095-1-kuba@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

arch/sh/include/asm/checksum_32.h

@@ -7,6 +7,7 @@
  */
 
 #include <linux/in6.h>
+#include <linux/uaccess.h>
 
 /*
  * computes the checksum of a memory block at buff, length len,