configs: Migrate the various SPL_BOOT_xxx choices for PowerPC

The non-CONFIG_SPL_FRAMEWORK SPL used on some PowerPC platforms have a
choice between CONFIG_SPL_NAND_BOOT, CONFIG_SPL_MMC_BOOT and
CONFIG_SPL_SPI_BOOT.  Migrate this to Kconfig

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/ls1021aiot_sdcard_defconfig b/configs/ls1021aiot_sdcard_defconfig
index 0925f1b..93eb834 100644
--- a/configs/ls1021aiot_sdcard_defconfig
+++ b/configs/ls1021aiot_sdcard_defconfig
@@ -5,7 +5,7 @@
 CONFIG_NR_DRAM_BANKS=1
 CONFIG_SPL=y
 CONFIG_AHCI=y
-CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPL_FSL_PBL,SD_BOOT,SD_BOOT_QSPI"
+CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SD_BOOT,SD_BOOT_QSPI"
 CONFIG_MISC_INIT_R=y
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_SPL_TEXT_BASE=0x10000000