spi25: Replace spi_read_chunked() with more abstract version

The new flashprog_read_chunked() takes a low-level reading function as
argument. This allows us to make use of the chunking with non-SPI read
functions.

Change-Id: Ica1b616e75e4e7682120928588e231c82cf4cf70
Signed-off-by: Nico Huber <nico.h@gmx.de>
Reviewed-on: https://review.sourcearcade.org/c/flashprog/+/74865
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
5 files changed