spi: Updates for v3.13 As well as the usual driver updates and cleanups there's a few improvements to the core here: - The start of some improvements to factor out more of the SPI message loop into the core. Right now this is just simplifying the code a bit but hopefully next time around we'll also have managed to roll out some noticable performance improvements which drivers can take advantage of. - Support for loading modules for ACPI enumerated SPI devices. - Managed registration for SPI controllers. - Helper for another common I/O pattern.