spi: nxp-xspi: Use reinit_completion() for repeated operations

spi: nxp-xspi: Use reinit_completion() for repeated operations

The driver currently calls init_completion() during every spi_mem_op.
Tchnically it may work, but it's not the recommended pattern.

According to the kernel documentation: Calling init_completion() on
the same completion object twice is most likely a bug as it
re-initializes the queue to an empty queue and enqueued tasks
could get "lost" - use reinit_completion() in that case, but be
aware of other races.

So moves the initial initialization to probe function and uses
reinit_completion() for subsequent operations.

Fixes: 29c8c00d9f9d ("spi: add driver for NXP XSPI controller")
Reviewed-by: Haibo Chen <haibo.chen@nxp.com>
Signed-off-by: Felix Gu <ustc.gu@gmail.com>
Link: https://patch.msgid.link/20260304-spi-nxp-v2-1-cd7d7726a27e@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>