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/pinetab_defconfig b/configs/pinetab_defconfig
index 0cc2414..4ecd241 100644
--- a/configs/pinetab_defconfig
+++ b/configs/pinetab_defconfig
@@ -8,3 +8,4 @@
 CONFIG_DRAM_ZQ=3881949
 CONFIG_MMC_SUNXI_SLOT_EXTRA=2
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
+CONFIG_SYS_PBSIZE=1024