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_win_defconfig b/configs/orangepi_win_defconfig
index 3b78ad7..9fce313 100644
--- a/configs/orangepi_win_defconfig
+++ b/configs/orangepi_win_defconfig
@@ -7,6 +7,7 @@
 CONFIG_MACPWR="PD14"
 CONFIG_SPL_SPI_SUNXI=y
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
+CONFIG_SYS_PBSIZE=1024
 CONFIG_SPI_FLASH_WINBOND=y
 CONFIG_PHY_REALTEK=y
 CONFIG_SUN8I_EMAC=y