Convert CONFIG_SF_DEFAULT_* to Kconfig

This converts the following to Kconfig:
  CONFIG_SF_DEFAULT_BUS
  CONFIG_SF_DEFAULT_CS
  CONFIG_SF_DEFAULT_MODE
  CONFIG_SF_DEFAULT_SPEED

I use moveconfig script and then manual check on generated u-boot.cfg
to solve the remaining issue.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
diff --git a/configs/mvebu_mcbin-88f8040_defconfig b/configs/mvebu_mcbin-88f8040_defconfig
index eb019c9..8c38722 100644
--- a/configs/mvebu_mcbin-88f8040_defconfig
+++ b/configs/mvebu_mcbin-88f8040_defconfig
@@ -44,6 +44,7 @@
 CONFIG_MMC_SDHCI=y
 CONFIG_MMC_SDHCI_XENON=y
 CONFIG_SPI_FLASH=y
+CONFIG_SF_DEFAULT_MODE=0
 CONFIG_SPI_FLASH_MACRONIX=y
 CONFIG_SPI_FLASH_SPANSION=y
 CONFIG_SPI_FLASH_STMICRO=y