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/ls1012a2g5rdb_tfa_defconfig b/configs/ls1012a2g5rdb_tfa_defconfig
index b54a388..4a65705 100644
--- a/configs/ls1012a2g5rdb_tfa_defconfig
+++ b/configs/ls1012a2g5rdb_tfa_defconfig
@@ -27,6 +27,7 @@
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_SYS_MAXARGS=64
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_MEMINFO=y
 CONFIG_CMD_MEMTEST=y