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/medcom-wide_defconfig b/configs/medcom-wide_defconfig
index cd039d2..f85dba5 100644
--- a/configs/medcom-wide_defconfig
+++ b/configs/medcom-wide_defconfig
@@ -15,6 +15,7 @@
 CONFIG_SYS_STDIO_DEREGISTER=y
 CONFIG_SYS_PROMPT="Tegra20 (Medcom-Wide) # "
 CONFIG_SYS_MAXARGS=64
+CONFIG_SYS_PBSIZE=2089
 # CONFIG_CMD_IMI is not set
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_GPIO=y