Convert CONFIG_SRIO_PCIE_BOOT_SLAVE to Kconfig

This converts the following to Kconfig:
   CONFIG_SRIO_PCIE_BOOT_SLAVE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/T2080QDS_SRIO_PCIE_BOOT_defconfig b/configs/T2080QDS_SRIO_PCIE_BOOT_defconfig
index cfc5f80..af8e73a 100644
--- a/configs/T2080QDS_SRIO_PCIE_BOOT_defconfig
+++ b/configs/T2080QDS_SRIO_PCIE_BOOT_defconfig
@@ -10,12 +10,12 @@
 CONFIG_MPC85xx=y
 CONFIG_TARGET_T2080QDS=y
 CONFIG_MPC85XX_HAVE_RESET_VECTOR=y
+CONFIG_SRIO_PCIE_BOOT_SLAVE=y
 CONFIG_MP=y
 CONFIG_FIT=y
 CONFIG_FIT_VERBOSE=y
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_OF_STDOUT_VIA_ALIAS=y
-CONFIG_SYS_EXTRA_OPTIONS="SRIO_PCIE_BOOT_SLAVE"
 CONFIG_DYNAMIC_SYS_CLK_FREQ=y
 CONFIG_BOOTDELAY=10
 CONFIG_USE_BOOTCOMMAND=y