ASoC: samsung: i2s: Remove unused gpios field from struct i2s

The 'gpios' field in 'struct i2s' is now unused, this change
seems to be missing in commit 0429ffef
("ASoC: samsung: Remove obsolete GPIO based DT pinmuxing").

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mark Brown <broonie@kernel.org>