Revert "configs: synquacer: Make U-Boot binary position independent"

This reverts commit f7e16bb0, since
the U-Boot doesn't boot if it is booted directly from SPI-NOR with
CONFIG_POSITION_INDEPENDENT=y. Unless fixing this issue, it is better
to revert this change.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu@linaro.org>