staging: rtl8712: Invert the test on check_fwstate() to reduce indentation

Negate if condition to be able to return immediately in case of error,
and then continue with the rest of the function
without extra indentation level.

This was found using the following Coccinelle script:

@disable neg_if@
expression e,E;
statement S;
@@

*if (e)
    S
    else { return -E; }

    @disable neg_if@
    expression e,E;
    statement S;
    identifier
    l;
    @@

    *if
(e)
    S
    else
{ rc = -E; goto l; }

Signed-off-by: Narcisa Ana Maria Vasile <narcisaanamaria12@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>