RFR: DIO-20 SPI: it is impossible to use external device

[boris kvartskhava]

issue: https://bugs.openjdk.java.net/browse/DIO-20
webrev: http://cr.openjdk.java.net/~onazarkina/DIO-20/

This change makes it possible to successfully perform expected I/O operation
with  jdk.dio.spibus.SPIDevice and jdk.dio.spibus.SPICompositeMessage.
A testing of previous change  was done on the implementation
that allowed repeated endTransaction() calls, as a result,
all SPIDevice.write/read/writeAndRead and SPICompositeMessage.transfer()
were throwing ISE.