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/ls1043aqds_sdcard_qspi_defconfig b/configs/ls1043aqds_sdcard_qspi_defconfig
index 391a0c6..bed7b45 100644
--- a/configs/ls1043aqds_sdcard_qspi_defconfig
+++ b/configs/ls1043aqds_sdcard_qspi_defconfig
@@ -54,6 +54,7 @@
 CONFIG_SPL_MPC8XXX_INIT_DDR=y
 CONFIG_SPL_WATCHDOG=y
 CONFIG_SYS_MAXARGS=64
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_GREPENV=y
 CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS=5