drivers: spi_nrfx_spim/spi: Fix initialization of CS GPIOs

This is a follow-up to commits 99daca9bba2136aff244b7ca36050a178c324036
and ae03c0a6bff293fdd8785b88026ee4e1bf163658.

nRF SPI driver shims cannot use devicetree instance indexes, they need
to use the DT_NODELABEL macro and SoC peripheral instance indexes.
Correct the macros used in initialization of CS GPIOs in those shims.

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