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/rut_defconfig b/configs/rut_defconfig
index 8e126e0..0b25a59 100644
--- a/configs/rut_defconfig
+++ b/configs/rut_defconfig
@@ -46,6 +46,7 @@
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_PROMPT="U-Boot# "
 CONFIG_SYS_MAXARGS=32
+CONFIG_SYS_PBSIZE=1049
 CONFIG_CMD_ASKENV=y
 CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS=10
 CONFIG_CMD_DFU=y