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/P1010RDB-PA_36BIT_NAND_defconfig b/configs/P1010RDB-PA_36BIT_NAND_defconfig
index b44264f..dc4d1c8 100644
--- a/configs/P1010RDB-PA_36BIT_NAND_defconfig
+++ b/configs/P1010RDB-PA_36BIT_NAND_defconfig
@@ -37,6 +37,7 @@
 CONFIG_TPL_MPC8XXX_INIT_DDR=y
 CONFIG_TPL_NAND_SUPPORT=y
 CONFIG_HUSH_PARSER=y
+CONFIG_SYS_PBSIZE=276
 CONFIG_CMD_IMLS=y
 CONFIG_SYS_EEPROM_PAGE_WRITE_BITS=3
 CONFIG_SYS_EEPROM_PAGE_WRITE_DELAY_MS=5