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/ge_b1x5v2_defconfig b/configs/ge_b1x5v2_defconfig
index 0096aca..fd1f3e3 100644
--- a/configs/ge_b1x5v2_defconfig
+++ b/configs/ge_b1x5v2_defconfig
@@ -44,6 +44,7 @@
 CONFIG_SPL_USB_SDP_SUPPORT=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_MAXARGS=32
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_MEMINFO=y