Adapt directory paths in Makefiles

Quantenna's kernel code references a lot of files that were located
outside the tree.  For example, they would use CFLAGS like -I../include.

We moved a number of files to new locations inside the Linux kernel tree
to avoid that the kernel build system references any files outside the
kernel tree. Now, we have to update Makefiles and symbolic links
accordingly. In some cases, it became necessary to change #include
24 files changed