spi: lantiq: Add support to Lightning Mountain SoC

Add support to SPI controller on Intel Atom based Lightning Mountain SoC
which reuses Lantiq SPI controller IP.

Signed-off-by: Dilip Kota <eswara.kota@linux.intel.com>
Link: https://lore.kernel.org/r/4d61a75381aca9479f9fc15d07a7b05534da6bb3.1594957019.git.eswara.kota@linux.intel.com


Signed-off-by: Mark Brown <broonie@kernel.org>