Convert CONFIG_SYS_CBSIZE to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_CBSIZE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/eb_cpu5282_internal_defconfig b/configs/eb_cpu5282_internal_defconfig
index 2f26923..93b860d 100644
--- a/configs/eb_cpu5282_internal_defconfig
+++ b/configs/eb_cpu5282_internal_defconfig
@@ -17,6 +17,7 @@
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_MISC_INIT_R=y
 # CONFIG_AUTO_COMPLETE is not set
+CONFIG_SYS_CBSIZE=1024
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_I2C=y
 # CONFIG_CMD_LOADB is not set