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/da850evm_defconfig b/configs/da850evm_defconfig
index 2374e39..a72c94e 100644
--- a/configs/da850evm_defconfig
+++ b/configs/da850evm_defconfig
@@ -17,6 +17,7 @@
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL_BOARD_INIT=y
+CONFIG_SPL_SPI_LOAD=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="U-Boot > "
 CONFIG_CRC32_VERIFY=y