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/opos6uldev_defconfig b/configs/opos6uldev_defconfig
index b56da14..8b0b4c3 100644
--- a/configs/opos6uldev_defconfig
+++ b/configs/opos6uldev_defconfig
@@ -37,6 +37,7 @@
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="BIOS> "
 CONFIG_SYS_MAXARGS=32
+CONFIG_SYS_PBSIZE=535
 CONFIG_CMD_CONFIG=y
 CONFIG_CMD_LICENSE=y
 CONFIG_CMD_BOOTZ=y