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/ls2080aqds_defconfig b/configs/ls2080aqds_defconfig
index bdea6bb..c4ba0d4 100644
--- a/configs/ls2080aqds_defconfig
+++ b/configs/ls2080aqds_defconfig
@@ -27,6 +27,7 @@
 CONFIG_BOOTCOMMAND="fsl_mc apply dpl 0x580d00000 && cp.b $kernel_start $kernel_load $kernel_size && bootm $kernel_load"
 CONFIG_RESET_PHY_R=y
 CONFIG_SYS_MAXARGS=64
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_IMLS=y
 CONFIG_CMD_GREPENV=y
 CONFIG_CMD_EEPROM=y