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/ls1046ardb_emmc_defconfig b/configs/ls1046ardb_emmc_defconfig
index 678c703..cfd2208 100644
--- a/configs/ls1046ardb_emmc_defconfig
+++ b/configs/ls1046ardb_emmc_defconfig
@@ -45,6 +45,7 @@
 CONFIG_SPL_MPC8XXX_INIT_DDR=y
 CONFIG_SPL_WATCHDOG=y
 CONFIG_SYS_MAXARGS=64
+CONFIG_SYS_PBSIZE=532
 CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS=5
 CONFIG_CMD_DM=y
 CONFIG_CMD_GPIO=y