spi_nxp_lpspi: Fix extra byte sent on v1 lpspi

This stupid errata will not leave me alone, here is another bandaid to
deal with an issue where an extra byte was being sent on version 1
LPSPIs due to the algorithm of filling NOPs when only RX is left was not
expecting the situation where the LPSPI actually consumed everything
from the fifo but is not sending it due to this ridiculous stalling errata.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>