staging: pi433: move get version func to where all other functions are

staging: pi433: move get version func to where all other functions are

As a convention for the pi433 driver, all routines that deals with the
rf69 chip are defined in the rf69.c file. There was an exception to the
rule in which the uC version verification was being done directly
elsewhere. While at it, the Version Register hardcoded value was
replaced with a pre-existing constant in the driver.

This patch adds rf69_get_version function to rf69.c

Signed-off-by: Paulo Miguel Almeida <paulo.miguel.almeida.rodenas@gmail.com>
Link: https://lore.kernel.org/r/20220108212728.GA7784@mail.google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>