staging: rts5208: combine ifs where possible

Join together chained if's where possible to lower the indentation
level.

In a lot of places of this code the indentation level is already very
high.
As a result, this patch increases the code flow and readability.

Signed-off-by: Giedrius Statkevičius <giedrius.statkevicius@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>