Convert CONFIG_QSPI_BOOT to Kconfig

This converts the following to Kconfig:
   CONFIG_QSPI_BOOT

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/ls1088ardb_qspi_defconfig b/configs/ls1088ardb_qspi_defconfig
index 5c42e7a..d593bc6 100644
--- a/configs/ls1088ardb_qspi_defconfig
+++ b/configs/ls1088ardb_qspi_defconfig
@@ -19,7 +19,7 @@
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS=" QSPI_BOOT"
+CONFIG_QSPI_BOOT=y
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyS0,115200 root=/dev/ram0 earlycon=uart8250,mmio,0x21c0500 ramdisk_size=0x3000000 default_hugepagesz=2m hugepagesz=2m hugepages=256"
 # CONFIG_USE_BOOTCOMMAND is not set