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/pic32mzdask_defconfig b/configs/pic32mzdask_defconfig
index 8c5934c..21f407c 100644
--- a/configs/pic32mzdask_defconfig
+++ b/configs/pic32mzdask_defconfig
@@ -16,6 +16,7 @@
 CONFIG_BOOTDELAY=5
 CONFIG_BOOTCOMMAND="run distro_bootcmd || run legacy_bootcmd"
 CONFIG_SYS_PROMPT="dask # "
+CONFIG_SYS_PBSIZE=1048
 # CONFIG_CMD_SAVEENV is not set
 CONFIG_LOOPW=y
 CONFIG_CMD_MEMINFO=y