Revert "Bias the placement of kernel pages at lower PFNs"

Revert "Bias the placement of kernel pages at lower PFNs"

This reverts commit 5adc5be7cd1bcef6bb64f5255d2a33f20a3cf5be.

Alexey Dobriyan reports that it causes huge slowdowns under some loads,
in his case a "mkfs.ext2" on a 30G partition.  With the placement bias,
the mkfs took over four minutes, with it reverted it's back to about ten
seconds for Alexey.

Reported-and-tested-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>