config: xea: Disable support for boot methods EXTLINUX and VBE

The XEA system (imx287 based) is not using support for EXTLINUX and VBE.
As those configuration options have been enabled by default with modern
Kconfig it is safe to explicitly disable them.

After that change the u-boot.img size has been reduced by ~16 KiB.

Signed-off-by: Lukasz Majewski <lukma@denx.de>
diff --git a/configs/imx28_xea_defconfig b/configs/imx28_xea_defconfig
index c6c6a03..a174bdb 100644
--- a/configs/imx28_xea_defconfig
+++ b/configs/imx28_xea_defconfig
@@ -29,6 +29,8 @@
 CONFIG_SPL_PAYLOAD="u-boot.img"
 CONFIG_FIT=y
 CONFIG_TIMESTAMP=y
+# CONFIG_BOOTMETH_EXTLINUX is not set
+# CONFIG_BOOTMETH_VBE is not set
 CONFIG_OF_BOARD_SETUP=y
 CONFIG_USE_BOOTARGS=y
 CONFIG_BOOTARGS="console=ttyAMA0,115200n8"