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/zc5202_defconfig b/configs/zc5202_defconfig
index faf9365..c1fec76 100644
--- a/configs/zc5202_defconfig
+++ b/configs/zc5202_defconfig
@@ -20,6 +20,7 @@
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL_EXT_SUPPORT=y
 CONFIG_SPL_I2C_SUPPORT=y
+CONFIG_SPL_SPI_LOAD=y
 CONFIG_CMD_MEMTEST=y
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_I2C=y