drivers/net/qlcnic: Use available error codes

drivers/net/qlcnic: Use available error codes

The error code is stored in the variable err, but it is the variable ret
that is returned instead.  So store the error code in ret.  Err is then
useless.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@r@
local idexpression x;
constant C;
@@

if (...) { ...
  x = -C
  ... when != x
(
  return <+...x...+>;
|
  return NULL;
|
  return;
|
* return ...;
)
}
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: David S. Miller <davem@davemloft.net>