staging: pi433: fix docs typos and references to previous struct names

In the comments there where some grammar mistakes and references to
struct names that have gotten renamed over time but not updated
in the comments.

Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@gmail.com>
Link: https://lore.kernel.org/r/20210828105633.GA8421@localhost.localdomain


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