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/MSI_Primo81_defconfig b/configs/MSI_Primo81_defconfig
index e77b007..de1b688 100644
--- a/configs/MSI_Primo81_defconfig
+++ b/configs/MSI_Primo81_defconfig
@@ -13,6 +13,7 @@
 CONFIG_VIDEO_LCD_BL_PWM="PH13"
 CONFIG_VIDEO_LCD_PANEL_MIPI_4_LANE_513_MBPS_VIA_SSD2828=y
 # CONFIG_SYS_MALLOC_CLEAR_ON_INIT is not set
+CONFIG_SYS_PBSIZE=1024
 CONFIG_AXP_DLDO1_VOLT=3300
 # CONFIG_REQUIRE_SERIAL_CONSOLE is not set
 CONFIG_USB_MUSB_HOST=y