spi: add EXPORT_SYMBOL_GPL(devm_spi_optimize_message)

spi: add EXPORT_SYMBOL_GPL(devm_spi_optimize_message)

devm_spi_optimize_message() is a public function and needs
EXPORT_SYMBOL_GPL.

Reported-by: Jonathan Cameron <jic23@kernel.org>
Closes: https://lore.kernel.org/linux-iio/20240624204424.6a91a5e4@jic23-huawei/
Fixes: d4a0055fdc22 ("spi: add devm_spi_optimize_message() helper")
Signed-off-by: David Lechner <dlechner@baylibre.com>
Link: https://patch.msgid.link/20240624-devm_spi_optimize_message-v2-1-58155c0180c2@baylibre.com
Signed-off-by: Mark Brown <broonie@kernel.org>