sunxi: dram_sun8i: Fix A33 memory initialization

While the exact problem is not known, based on discussion between
Philipp Tomsich and André Przywara it is guessed that exit self-refresh
timing is not set with correct value. There may be implicit enter or
exit Self-Refresh anywhere as part of some training phase.

In ZynqMP register guide [1], which is close to the various
Allwinner DRAM controllers, tXSDLL is bits [14:8], while the non-DLL
tXS is bits [6:0]: Self refresh exit delay. So it could be safely
increased and it only affects the time after the self-refresh “exit”,
which happens only after (re-)initialisation.

There was no document for cpu in question so based on oscilloscope
readings [2][3] and observed result by comparing allwinner architecture.
So set it same as  Allwinner H5 silicon.

Before this patch, failure rate of was 7%.

This was tested on A33 allwinner cpu, dual rank connection connected
with two MT41K512M16HA-125:A memory model. Memory is configured as DDR3
1.5V

And also this is tested in A33-OLinuXino dev board.

[1] https://www.xilinx.com/html_docs/registers/ug1087/ddrc___dramtmg8.html
[2] https://ibb.co/R70zmyS
[3] https://ibb.co/HVVCGQ8



Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>
Signed-off-by: Shyam Saini <shyam.saini@amarulasolutions.com>
Acked-by: Jagan Teki <jagan@openedev.com>