staging: vt6655: Change return type of function and remove variable

Remove return variable bResult from function CARDbRadioPowerOff and
change the return type of the function to void as it always returns true
and the return value is never stored nor checked when called.
Issue found with Coccinelle.

Signed-off-by: Nishka Dasgupta <nishkadg.linux@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>