ASoC: cs42l51: re-hook of_match_table pointer

In commit a1253ef6 ("ASoC: cs42l51: split i2c from codec driver"),
the I2C part of the CS42L51 was moved to a separate file, but the
definition of the of_device_id array was left in the driver file
itself, no longer connected to the platform_driver structure using the
.of_match_table pointer.

This commit exports the of_device_id array in cs42l51, and uses it as
.of_match_able in cs42l51-i2c.c. This solution was suggested by Brian
Austin.

Fixes: a1253ef6 ("ASoC: cs42l51: split i2c from codec driver")
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Brian Austin <brian.austin@cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: <stable@vger.kernel.org>