ddr: altera: Clean up rw_mgr_mem_calibrate_read_test_patterns()

ddr: altera: Clean up rw_mgr_mem_calibrate_read_test_patterns()

Rework this function such that the code is more readable. Zap
unused parameter "num_tries" while at it. Also wrap parameter
"bit_chk" into this function as it's value is not used outside.
Finally, fix the return value from this function to match the
common expectation, where 0 means success.

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