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/Sinlinx_SinA33_defconfig b/configs/Sinlinx_SinA33_defconfig
index 4eb5300..0f30dfc 100644
--- a/configs/Sinlinx_SinA33_defconfig
+++ b/configs/Sinlinx_SinA33_defconfig
@@ -13,6 +13,7 @@
 CONFIG_VIDEO_LCD_BL_EN="PH6"
 CONFIG_VIDEO_LCD_BL_PWM="PH0"
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
+CONFIG_SYS_PBSIZE=1024
 CONFIG_CMD_DFU=y
 CONFIG_DFU_RAM=y
 CONFIG_FASTBOOT_CMD_OEM_FORMAT=y