Enable SPI communication between FMC and FPGA
Both current (as at commit ac61b614) MMC to FPGA signals in the MMC are alreadi in MOSI and MISO lines. If we connect the currently available pin 34 (SCK in this SPI port) to the FPGA we could establish full SPI communication for current and future purposes. AE32, which is available and near these signals in the FPGA, could be used for SCK input (or output, this may be defined by MMC and gateware developers later).