Convert CONFIG_SYS_PBSIZE to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_PBSIZE

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/rastaban_defconfig b/configs/rastaban_defconfig
index 2f10ad0..ae57cd4 100644
--- a/configs/rastaban_defconfig
+++ b/configs/rastaban_defconfig
@@ -47,6 +47,7 @@
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="U-Boot# "
 CONFIG_SYS_MAXARGS=32
+CONFIG_SYS_PBSIZE=1049
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_DFU=y
 # CONFIG_CMD_FLASH is not set