ddr: altera: Clean up sdr_find_window_centre() part 1

ddr: altera: Clean up sdr_find_window_centre() part 1

Clean up the arguments of this function. Most of the pointers
passed into the function are either not needed at all, or can
be passed as value instead of reference. Also fix the broken
multiline debug strings. No functional change.

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