staging: zram: add dependency for swapon()

So zram won't work with swap now and swap makes problems
according to @Quarx. Add a simple trick here and make a
dependency for swapon which is only available if swapfile.c
is compiled.

This is only a temporary solution. Also cleanup some errors
and things from yesterday, i am still not happy with
shrink_page_list() since our implementation has slighty changed
arguments, but it seems to work just fine.

Signed-off-by: Blechd0se <alex.christ@hotmail.de>
defconfig: enable ram_console for 4.2

Enable the android ram console.
This is the first step to fix /proc/last_kmsg

Signed-off-by: Blechd0se <alex.christ@hotmail.de>
staging: android: some ram_console fixes

We should get ram console working since it has a
powerful debug-feature; /proc/last_kmsg

Squashed some upstream fixes, now we need to crash
the kernel ;)

Signed-off-by: Blechd0se <alex.christ@hotmail.de>