Remove empty file remnants that were left in the tree by mistake

Noted by various people (Sam, Jeff, Roland..)

Commit 58b7983d intended to remove the
xfs "Makefile-linux-2.6" file, but it was mistakenly still left in the
tree as a empty file, and would cause git to correctly complain about a
tracked file being removed after a "make distclean" (which removes empty
files as garbage).

And the asm-x86/desc_64.h file was supposed to be removed by commit
c81c6ca4, but instead stayed around
containing just a single newline.

Get rid of them both properly.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>