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/Nintendo_NES_Classic_Edition_defconfig b/configs/Nintendo_NES_Classic_Edition_defconfig
index b660234..84b36a0 100644
--- a/configs/Nintendo_NES_Classic_Edition_defconfig
+++ b/configs/Nintendo_NES_Classic_Edition_defconfig
@@ -9,6 +9,7 @@
 CONFIG_USB0_VBUS_DET="AXP0-VBUS-DETECT"
 CONFIG_AXP_GPIO=y
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
+CONFIG_SYS_PBSIZE=1024
 # CONFIG_CMD_FLASH is not set
 CONFIG_CMD_MTDPARTS=y
 # CONFIG_MMC is not set