ddr: socfpga: Clean up ddr_setup()

ddr: socfpga: Clean up ddr_setup()

Replace the current rather convoluted code using ad-hoc polling
mechanism with a more straightforward code. Use wait_for_bit_le32()
to poll the DDRCALSTAT register instead of local reimplementation.
It makes no sense to pull for 5 seconds before giving up and trying
to restart the EMIF, so instead wait 500 mSec for the calibration to
complete and if this fails, restart the EMIF and try again. Perform
this 32 times instead of 3 times as the original code did.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Chin Liang See <chin.liang.see@intel.com>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Cc: Tien Fong Chee <tien.fong.chee@intel.com>