split floppy.c into two modules

But now this doesn't work...

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Makefile: represent dependencies properly

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Makefile: add debug, cross-compile definitions

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
move-ctrl: add missing #include

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
floppy: fix array-size bug

This should have been subtraction, not addition. What a &^%$^#%@$ bug to
have been scratching my head over...

Signed-off-by: Brian Norris <computersforpeace@gmail.com>