Convert CONFIG_ENV_SPI_BUS et al to Kconfig

This converts the following to Kconfig:
   CONFIG_ENV_SPI_BUS
   CONFIG_ENV_SPI_CS
   CONFIG_ENV_SPI_MAX_HZ
   CONFIG_ENV_SPI_MODE

As part of this, we use Kconfig to provide the defaults now that were
done in include/spi_flash.h.  We also in some cases change from using
CONFIG_ENV_SPI_FOO to CONFIG_SF_DEFAULT_FOO as those were the values in
use anyhow as ENV was not enabled.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/net/fm/fm.c b/drivers/net/fm/fm.c
index 7d51be1..f825612 100644
--- a/drivers/net/fm/fm.c
+++ b/drivers/net/fm/fm.c
@@ -387,8 +387,8 @@
 		struct udevice *new;
 
 		/* speed and mode will be read from DT */
-		ret = spi_flash_probe_bus_cs(CONFIG_ENV_SPI_BUS,
-					     CONFIG_ENV_SPI_CS, 0, 0, &new);
+		ret = spi_flash_probe_bus_cs(CONFIG_SF_DEFAULT_BUS,
+					     CONFIG_SF_DEFAULT_CS, 0, 0, &new);
 
 		ucode_flash = dev_get_uclass_priv(new);
 #else
@@ -474,7 +474,7 @@
 	struct udevice *new;
 
 	/* speed and mode will be read from DT */
-	ret = spi_flash_probe_bus_cs(CONFIG_ENV_SPI_BUS, CONFIG_ENV_SPI_CS,
+	ret = spi_flash_probe_bus_cs(CONFIG_SF_DEFAULT_BUS, CONFIG_SF_DEFAULT_CS,
 				     0, 0, &new);
 
 	ucode_flash = dev_get_uclass_priv(new);