spl: spi: Move CONFIG_SPL_SPI_LOAD to Kconfig

Add Kconfig entry for CONFIG_SPL_SPI_LOAD symbol and move all
configurations using it to Kconfig.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Tom Rini <trini@konsulko.com>
diff --git a/configs/socfpga_arria10_defconfig b/configs/socfpga_arria10_defconfig
index cd414fe..e5984f2 100644
--- a/configs/socfpga_arria10_defconfig
+++ b/configs/socfpga_arria10_defconfig
@@ -13,6 +13,7 @@
 CONFIG_DEFAULT_FDT_FILE="socfpga_arria10_socdk_sdmmc.dtb"
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_SPL_FPGA_SUPPORT=y
+CONFIG_SPL_SPI_LOAD=y
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_GREPENV=y
 # CONFIG_CMD_FLASH is not set