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/ls1021atwr_sdcard_ifc_SECURE_BOOT_defconfig b/configs/ls1021atwr_sdcard_ifc_SECURE_BOOT_defconfig
index 28db528..979878d 100644
--- a/configs/ls1021atwr_sdcard_ifc_SECURE_BOOT_defconfig
+++ b/configs/ls1021atwr_sdcard_ifc_SECURE_BOOT_defconfig
@@ -14,7 +14,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPL_FSL_PBL,SD_BOOT"
+CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SD_BOOT"
 CONFIG_BOOTDELAY=0
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 root=/dev/ram0"