[MTD] Make functions static, include header files with prototypes

This patch contains the following possible cleanups:
- every file should #include the headers containing the prototypes for
  it's global functions
- make needlessly global functions static

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>