* #1623, implementing suggested change

Splitted suggested fix issue #1623 in a header and source part. Dit not completely dive into the code.
Giving data twice as parameter feels wrong, but it compiles, and i can succesfully use the W5500 with SPI with this fix.
Doesn't compile without.

* #1623, implementing suggested change SPI.h/cpp

Splitted suggested fix issue #1623 in a header and source part. Dit not completely dive into the code.
Giving data twice as parameter feels wrong, but it compiles, and i can succesfully use the W5500 with SPI with this fix.
Doesn't compile without.