spi: pxa2xx: Do not detect number of enabled chip selects on Intel SPT

BugLink: http://bugs.launchpad.net/bugs/1584912

commit 66ec246e upstream.

Certain Intel Sunrisepoint PCH variants report zero chip selects in SPI
capabilities register even they have one per port. Detection in
pxa2xx_spi_probe() sets master->num_chipselect to 0 leading to -EINVAL
from spi_register_master() where chip select count is validated.

Fix this by not using SPI capabilities register on Sunrisepoint. They don't
have more than one chip select so use the default value 1 instead of
detection.

Fixes: 8b136baa ("spi: pxa2xx: Detect number of enabled Intel LPSS SPI chip select signals")
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/spi/spi-pxa2xx.c

@@ -111,7 +111,7 @@ static const struct lpss_config lpss_platforms[] = {
 		.reg_general = -1,
 		.reg_ssp = 0x20,
 		.reg_cs_ctrl = 0x24,
-		.reg_capabilities = 0xfc,
+		.reg_capabilities = -1,
 		.rx_threshold = 1,
 		.tx_threshold_lo = 32,
 		.tx_threshold_hi = 56,