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/ls1046aqds_SECURE_BOOT_defconfig b/configs/ls1046aqds_SECURE_BOOT_defconfig
index 3e61619..fe1a601 100644
--- a/configs/ls1046aqds_SECURE_BOOT_defconfig
+++ b/configs/ls1046aqds_SECURE_BOOT_defconfig
@@ -35,6 +35,7 @@
 CONFIG_BOOTCOMMAND="run distro_bootcmd; run nor_bootcmd; env exists secureboot && esbc_halt;;"
 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