It seems the comment for GetDevAddress was copied from GetUniqueId, but
not changend sufficiently to be correct.

These warnings are caused because frequencies are stored as `uint32_t`,
which is `unsigned long`, while the printf format expects `int`. In
practice, this does not actually cause problems, since on STM32 gcc
`long` and `int` are both 32-bits and frequencies are never large enough
to cause signed vs unsigned ambiguity.

Since printf has no format specifiers for e.g. uint32_t (libc does have
some macros for this, but those really hurt readability), this is tricky
to fix in a portable way (other architectures or compilers might have
`uint32_t` equal to `unsigned int` instead of `unsigned long`), this fix
just casts the frequency to `unsigned` before passing it to printf (and
for good measure, also convert the specifier from `%d` to `%u`). This
does mean this printing will break if `int` is not at least 32-bits
(e.g. on AVR), but given the scope of this library, that should be
acceptable.

This adds some more details about RX and TX bytes and TX config. There
is also some code for RX config, but to minimize the impact on RX
timing, that is commented out.