Repair broken SPI flash images from U Boot

Stop U-Boot to prompt and run the following (assuming we want to update the rescue image and we have the image on USB flash disk in path usr/share/rescue-image/image.fit.lzma).

=> usb start
=> load usb 0 $kernel_addr_r usr/share/rescue-image/image.fit.lzma
6152382 bytes read in 477 ms (12.3 MiB/s)
=> load usb 0 $kernel_addr_r usr/share/rescue-image/image.fit.lzma
6152382 bytes read in 477 ms (12.3 MiB/s)
=> usb start
=> sf probe
SF: Detected mx25l6405d with page size 256 Bytes, erase size 4 KiB, total 8 MiB
=> sf update $kernel_addr_r 0x100000 0x700000
device 0 offset 0x100000, size 0x700000