base-files: remove the unnecessary /media/xxx directories

base-files: remove the unnecessary /media/xxx directories

A few directories under /media were created by default, /media/card,
/media/ram, /media/realroot, etc.

These directories actually have no real usage now, thus removing them.

The /media/ram entry in the fstab is also removed, as mounting a tmpfs
over /media/ram in our system brings no benefit.

Note that a duplicate '/mnt' entry in dirs755 are also removed.

[Yocto #4774]

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>