memory.txt: remove stray information

Andi removed some outedated documentation from Documentation/memory.txt
back in 2009 by commit 3b2b9a87 ("Documentation/memory.txt: remove
some very outdated recommendations"), but the resulting document is not
in a nice shape either.

It seems to me like we are not losing anything by completely removing the
file now.
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/memory.txt

-There are several classic problems related to memory on Linux
-systems.
-
-	1) There are some motherboards that will not cache above
-	   a certain quantity of memory.  If you have one of these
-	   motherboards, your system will be SLOWER, not faster
-	   as you add more memory.  Consider exchanging your 
-           motherboard.
-
-All of these problems can be addressed with the "mem=XXXM" boot option
-(where XXX is the size of RAM to use in megabytes).  
-It can also tell Linux to use less memory than is actually installed.
-If you use "mem=" on a machine with PCI, consider using "memmap=" to avoid
-physical address space collisions.
-
-See the documentation of your boot loader (LILO, grub, loadlin, etc.) about
-how to pass options to the kernel.
-
-There are other memory problems which Linux cannot deal with.  Random
-corruption of memory is usually a sign of serious hardware trouble.
-Try:
-
-	* Reducing memory settings in the BIOS to the most conservative 
-          timings.
-
-	* Adding a cooling fan.
-
-	* Not overclocking your CPU.
-
-	* Having the memory tested in a memory tester or exchanged
-	  with the vendor. Consider testing it with memtest86 yourself.
-	
-	* Exchanging your CPU, cache, or motherboard for one that works.