linux_mtd: Switch fopen() to open() for MTD devices

There's no benefit to using the higher level "FILE *" for file
operations for writing to mtd devices. Let's move to the lower level
ones which matches the kernel more closely.

For background here, using the higher level "FILE *" operations:
* Gives us access to a bunch of higher level functions for file reading
  like fscanf(), fgets(), fgetc(), fflush(), ... Many of those are
  just wrappers for the lower level operations. Those that aren't
  (like fscanf) are things that we don't need for dealing with flash.
* By default provides higher performance by buffering things behind
  our back. This is actually something we specifically _don't_ want
  because if we send a command like "erase" the C library doesn't know
  to throw away its buffers. NOTE: we actually already turned off
  buffering in commit a2f2f3f5ee1b ("linux_mtd: Disable buffering on
  the mtd device").

So in summary: this change is a no-op but simply removes a layer of
overhead / translation that we just don't need.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Change-Id: Ifeb00b049ba5aa0bc8fdc591ac1f9861ad5d428d
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M linux_mtd.c
1 file changed, 16 insertions(+), 17 deletions(-)