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/mx6qsabrelite_defconfig b/configs/mx6qsabrelite_defconfig
index 31e8d32..551057f 100644
--- a/configs/mx6qsabrelite_defconfig
+++ b/configs/mx6qsabrelite_defconfig
@@ -26,6 +26,7 @@
 CONFIG_BOARD_EARLY_INIT_F=y
 CONFIG_MISC_INIT_R=y
 CONFIG_SYS_MAXARGS=32
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_MEMTEST=y
 CONFIG_SYS_ALT_MEMTEST=y
 # CONFIG_CMD_FLASH is not set