spi: make falcon-spi bool

Falcon spi accesses some ebu functions which are not exported and can
not be accessed when build as module. Make this module bool instead.
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Acked-by: Thomas Langer <thomas.langer@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/Kconfig

@@ -263,7 +263,7 @@ config SPI_EP93XX
 	  mode.
 
 config SPI_FALCON
-	tristate "Falcon SPI controller support"
+	bool "Falcon SPI controller support"
 	depends on SOC_FALCON
 	help
 	  The external bus unit (EBU) found on the FALC-ON SoC has SPI