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/qemu-x86_defconfig b/configs/qemu-x86_defconfig
index 6010b61..b9ab180 100644
--- a/configs/qemu-x86_defconfig
+++ b/configs/qemu-x86_defconfig
@@ -19,6 +19,7 @@
 CONFIG_DISPLAY_BOARDINFO_LATE=y
 CONFIG_LAST_STAGE_INIT=y
 CONFIG_PCI_INIT_R=y
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_CPU=y
 CONFIG_CMD_BOOTEFI_SELFTEST=y
 CONFIG_CMD_NVEDIT_EFI=y