staging: rtl8192u: Using comparison to true is error prone

fix below issue reported by checkpatch:

CHECK: Using comparison to true is error prone
CHECK: Using comparison to false is error prone

Signed-off-by: John Oldman <john.oldman@polehill.co.uk>
Link: https://lore.kernel.org/r/20200516163327.9197-1-john.oldman@polehill.co.uk


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>