Merge tag 'spi-devm-optimize' into togreg

spi: add devm_spi_optimize_message() helper

Helper from David Lechner <dlechner@baylibre.com>:

    In the IIO subsystem, we are finding that it is common to call
    spi_optimize_message() during driver probe since the SPI message
    doesn't change for the lifetime of the driver. This patch adds a
    devm_spi_optimize_message() helper to simplify this common pattern.