soc: arm: nxp_lpc: Convert from Kconfig to DT_NODELABEL

As we phase out per instance Kconfig symbols convert to utilize
DT_NODELABEL for SPI and I2C instances instead.

Also updated comments to change from FLEXCOMM8 to HSLSPI.

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>