Upgrade the Zynq driver to recognise and use drives larger than 64GB

[htibosch]

Until now, FreeRTOS+FAT was never really tested on drives larger than 64GB.

This PR is adding a Xilinx Zynq driver which can recognise and use an SD-card of 128GB. Therefore I upgraded the driver sources that are provided by Xilinx in their 2019.03 release.

I adapter these sources to use interrupts ( in stead of polling ), which makes them more efficient.

Then, as a test, I created 3 equal partitions and mounted them all in the same tree:

/
/part_1
/part_2

The first partition was represented at the root directory. I tested by writing and reading files on each partition and have the drive checked by dosfsck under Ubuntu.

I had to make some more adaptations: each instance of an FF_Disk_t now gets its own copy of CacheMemoryInfo_t. This is uncached caching memory ( i.e. uncached by the CPU ). It can be passed to DMA, without the need to invalidate or refresh.

Another change had to be made to ff_format.c : only in partition 0, the FAT can be moved into the second 4MB erase block ( see comment in source code ).

I gave the new Zyn port a new directory: portable\Zynq.2019.3. Let's rename it as soon as it has proven to be as stable as the existing 2015.03 Zynq driver. I will also keep on testing it.
Hein