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/orangepi_zero_plus_defconfig b/configs/orangepi_zero_plus_defconfig
index f3ecf35..e7d6b5d 100644
--- a/configs/orangepi_zero_plus_defconfig
+++ b/configs/orangepi_zero_plus_defconfig
@@ -7,6 +7,7 @@
 CONFIG_DRAM_ZQ=3881977
 # CONFIG_DRAM_ODT_EN is not set
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
+CONFIG_SYS_PBSIZE=1024
 CONFIG_SUN8I_EMAC=y
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_OHCI_HCD=y