auxdisplay: ks0108: remove superfluous header files

ks0108.c doesn't use any macro or function declared in
linux/fs.h, linux/io.h and linux/uaccess.h. Thus,
these files can be removed from ks0108.c safely without
affecting the compilation.

Signed-off-by: Mianhan Liu <liumh1@shanghaitech.edu.cn>
[reworded]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>