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_lpuart_defconfig b/configs/ls1043aqds_lpuart_defconfig
index 2d44d1e..c32a5f2 100644
--- a/configs/ls1043aqds_lpuart_defconfig
+++ b/configs/ls1043aqds_lpuart_defconfig
@@ -37,6 +37,7 @@
 CONFIG_ARCH_MISC_INIT=y
 CONFIG_MISC_INIT_R=y
 CONFIG_SYS_MAXARGS=64
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_GREPENV=y