tests: drivers: i2s: Add test for 8ch, 32bit, 48k TDM

Add test case where TDM is tested with 8 channels,
32 bit word size and 48k sample rate.

Add Kconfig that enables test skip if the driver supports
8 channels but fails in this configuration.

Signed-off-by: Sebastian Głąb <sebastian.glab@nordicsemi.no>