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/Mele_M5_defconfig b/configs/Mele_M5_defconfig
index f2ee3b1..79ea3f0 100644
--- a/configs/Mele_M5_defconfig
+++ b/configs/Mele_M5_defconfig
@@ -10,6 +10,7 @@
 CONFIG_AHCI=y
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
 CONFIG_SPL_I2C=y
+CONFIG_SYS_PBSIZE=1024
 CONFIG_SCSI_AHCI=y
 CONFIG_SYS_I2C_MVTWSI=y
 CONFIG_SYS_I2C_SLAVE=0x7f