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/kmeter1_defconfig b/configs/kmeter1_defconfig
index 9fc8f0a..58813b7 100644
--- a/configs/kmeter1_defconfig
+++ b/configs/kmeter1_defconfig
@@ -139,6 +139,7 @@
 CONFIG_MISC_INIT_R=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_MAXARGS=32
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_ASKENV=y
 CONFIG_CMD_GREPENV=y