staging: pi433: rf69.c: Replace macros READ_REG and WRITE_REG with smarter functions

To increase the readability of the register accesses, the abstraction
of the helpers was increased from simple read and write to set bit,
clear bit and read modify write bit.

Annotation: This patch contains a lot of long lines and camel case
var names. These long lines and camel case vars weren't introduced
by this patch, but were long and camel cased before.

Signed-off-by: Marcus Wolf <linux@wolf-entwicklungen.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>