staging: rts5208: remove redundant retval status check

staging: rts5208: remove redundant retval status check

The retval status checks in the proceeding do loop return out
of function ms_read_attritbute_info if there is an error
condition,  thus we never reach the end of the loop with
retval failed status.  Therefore, the retval status check
at end of the do loop is redundant and can be removed.

Detected with CoverityScan, CID#143000 ("Logically dead code")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>