[U2+L] Save REU memory failed on USB drive

[xinteksik]

Save REU memory failed on USB drive.

With size 32GB and 64GB - bug

• FAT32 or exFAT
• cluster 64kB and more
• log-bug.log

Small USB drive - works

• with size 2GB
• cluster 4kB

Symptoms:

• no progress bar when saving, but led blinking
• after few seconds Bytes saved: 0 ($00000000)
• connected USB drive disappears
• 64GB exFAT with 32kB cluster (max) - works

[GideonZ]

This is absolutely NOT the same issue as #416

[xinteksik]

OK OK, sorry

But cluster size over 32kB is that problem, right?

Problem only for save REU images.