Transfer rate: KB/S reading in ncurses examples slightly out of whack

[TMRh20]

The

RF24Gateway/examples/ncurses/RF24Gateway_ncurses.cpp

Line 87 in 4729fc8

size_t bRX;

&

RF24Gateway/examples/ncurses/RF24Gateway_ncurses.cpp

Line 88 in 4729fc8

size_t bTX;

vars should be floats, since the calculation using them is done with floats.

If a lot of data is transferred, eventually the KB/S reading will be incorrect otherwise.

While we are at it, the line

RF24Gateway/examples/ncurses/RF24Gateway_ncurses.cpp

Line 603 in 4729fc8

float TKBS = bytesRNow > 0 ? bytesTNow / updateRate : 0.0;

should read bytesTNow