sequencer.c

Factor out common code from rw_mgr_mem_calibrate_writes_center()
and rw_mgr_mem_calibrate_vfifo_center() for searching for the
right edge of the window. The code is almost identical, so pull
it into separate function and cater for the minor differences.

Signed-off-by: Marek Vasut <marex@denx.de>