staging: gasket: apex_clock_gating simplify logic, reduce indentation

Collapse together two checks and return immediately, avoid conditional
indentation for most of function code.

Reported-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Simon Que <sque@chromium.org>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>