drivers: i2s: i2s_mcux_sai: fix logging statements for k_mem_slab

Since 2f003e59 reworked the structure of k_mem_slab information fields,
we need to update the logging statements in the i2s_mcux_sai driver to
access these fields correctly.

Fixes #63527

Signed-off-by: Daniel DeGrasse <daniel.degrasse@nxp.com>