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/ls1088aqds_defconfig b/configs/ls1088aqds_defconfig
index c3990d6..8e8caa4 100644
--- a/configs/ls1088aqds_defconfig
+++ b/configs/ls1088aqds_defconfig
@@ -36,6 +36,7 @@
 CONFIG_RESET_PHY_R=y
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_MAXARGS=64
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_GREPENV=y
 CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS=5
 CONFIG_CMD_MEMINFO=y