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/udoo_defconfig b/configs/udoo_defconfig
index 9980a6e..d3b49bf 100644
--- a/configs/udoo_defconfig
+++ b/configs/udoo_defconfig
@@ -26,6 +26,7 @@
 CONFIG_SPL_I2C=y
 CONFIG_SPL_WATCHDOG=y
 CONFIG_SYS_MAXARGS=32
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_MMC=y
 # CONFIG_CMD_PINMUX is not set