mm,x86: remove debug_pagealloc_enabled

mm,x86: remove debug_pagealloc_enabled

When (no)bootmem finishes its operation, it passes pages to the buddy
allocator.  Since debug_pagealloc_enabled is not set, we will not protect
these pages, which is not what we want with CONFIG_DEBUG_PAGEALLOC=y.

To fix this, remove debug_pagealloc_enabled.  That variable was introduced
by commit 12d6f21e ("x86: do not PSE on CONFIG_DEBUG_PAGEALLOC=y") to get
more CPA (change page attribude) code testing.  But currently we have
CONFIG_CPA_DEBUG, which tests CPA.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>