csum_partial_copy_nocheck(): drop the last argument

It's always 0.  Note that we theoretically could use ~0U as well -
result will be the same modulo 0xffff, _if_ the damn thing did the
right thing for any value of initial sum; later we'll make use of
that when convenient.

However, unlike csum_and_copy_..._user(), there are instances that
did not work for arbitrary initial sums; c6x is one such.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/arm/include/asm/checksum.h

@@ -35,7 +35,7 @@ __wsum csum_partial(const void *buff, int len, __wsum sum);
  */
 
 __wsum
-csum_partial_copy_nocheck(const void *src, void *dst, int len, __wsum sum);
+csum_partial_copy_nocheck(const void *src, void *dst, int len);
 
 __wsum
 csum_partial_copy_from_user(const void __user *src, void *dst, int len, __wsum sum, int *err_ptr);