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/meesc_defconfig b/configs/meesc_defconfig
index c549fa2..d08acb6 100644
--- a/configs/meesc_defconfig
+++ b/configs/meesc_defconfig
@@ -17,6 +17,7 @@
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_MISC_INIT_R=y
 CONFIG_HUSH_PARSER=y
+CONFIG_SYS_PBSIZE=532
 # CONFIG_CMD_BDI is not set
 CONFIG_CMD_BOOTZ=y
 # CONFIG_CMD_LOADS is not set