spi: brcmstb-qspi: Broadcom settop platform driver

Adding the settop SoC platfrom driver, this driver is compatible
with the settop MSPI+BSPI and MSPI only blocks implemented on the
SoCs. Driver calls the spi-bcm-qspi probe(), remove() and pm_ops.

Signed-off-by: Kamal Dasu <kdasu.kdev@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>