staging: rtl8712: Invert if statements to reduce indentation level

Invert if statements to be able to return immediately in case of error,
and to avoid additional else branch, and then continue with the rest
of the function without excessive indentation.

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>