Log Message:
This should extract generic after the architecture specific.
Because many of the architecture specific versions of same files
reference the "asm-generic" version. So just overwrite with
real version. (I don't know how this could have ever
worked in the first place.)

Also create symlink for asm-generic while at it, because a few
headers still reference asm-generic (like cpumask.h, errno.h,
and ide.h).

(Another idea would be to just install both sets of headers
in two different directories.)