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/trats_defconfig b/configs/trats_defconfig
index 5990dc1..267ca86 100644
--- a/configs/trats_defconfig
+++ b/configs/trats_defconfig
@@ -23,6 +23,7 @@
 CONFIG_SYS_CONSOLE_INFO_QUIET=y
 CONFIG_MISC_INIT_R=y
 CONFIG_SYS_PROMPT="Trats # "
+CONFIG_SYS_PBSIZE=1024
 # CONFIG_CMD_XIMG is not set
 CONFIG_CMD_THOR_DOWNLOAD=y
 CONFIG_CMD_DFU=y