drivers: spi_nrfx_spi[m]: Handle transaction timeouts properly

Add code that acts accordingly when a transaction does not complete
in the expected time. It makes sure that the transaction is aborted
so that no unexpected interrupt occurs afterwards and it also cleans
up after that abort so that the driver can handle further requests.

Signed-off-by: Andrzej Głąbek <andrzej.glabek@nordicsemi.no>