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/xilinx_zynqmp_virt_defconfig b/configs/xilinx_zynqmp_virt_defconfig
index 8b1529d..6981497 100644
--- a/configs/xilinx_zynqmp_virt_defconfig
+++ b/configs/xilinx_zynqmp_virt_defconfig
@@ -41,6 +41,7 @@
 CONFIG_SPL_ATF=y
 CONFIG_SPL_ATF_NO_PLATFORM_PARAM=y
 CONFIG_SYS_MAXARGS=64
+CONFIG_SYS_PBSIZE=2073
 CONFIG_CMD_BOOTMENU=y
 CONFIG_CMD_THOR_DOWNLOAD=y
 CONFIG_CMD_NVEDIT_EFI=y