spi: synquacer: Add HSSPI SPI controller driver for SynQuacer

spi: synquacer: Add HSSPI SPI controller driver for SynQuacer

This is a driver for the HSSPI SPI controller on SynQuacer SoC.
The HSSPI has command sequence mode (memory mapped) and
direct mode (FIFO access). The driver will operate it under
the direct mode. And before booting OS, it switch back to the
command sequence mode since that is compatible with default
EDK2 behavior.

Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu@linaro.org>