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/tqma6s_mba6_mmc_defconfig b/configs/tqma6s_mba6_mmc_defconfig
index 96e4d29..9400c64 100644
--- a/configs/tqma6s_mba6_mmc_defconfig
+++ b/configs/tqma6s_mba6_mmc_defconfig
@@ -17,6 +17,7 @@
 CONFIG_DEFAULT_FDT_FILE="imx6dl-mba6x.dtb"
 CONFIG_HUSH_PARSER=y
 CONFIG_SYS_MAXARGS=32
+CONFIG_SYS_PBSIZE=532
 CONFIG_CMD_BOOTZ=y
 CONFIG_CMD_EEPROM=y
 CONFIG_SYS_I2C_EEPROM_ADDR_LEN=2