memblock: add error return when CONFIG_HAVE_MEMBLOCK is not set

On larger systems, information in the kernel log is lost because there is
so much early text printed, that it overflows the static log buffer before
the log_buf_len kernel parameter can be processed, and a bigger log buffer
allocated.

Distros are relunctant to increase memory usage by increasing the size of
the static log buffer, so minimize the problem by allocating the new log
buffer as early as possible.

This patch:

Add an error return if CONFIG_HAVE_MEMBLOCK is not set instead of having
to add #ifdef CONFIG_HAVE_MEMBLOCK around blocks of code calling that
function.

Signed-off-by: Mike Travis <travis@sgi.com>
Cc: Yinghai Lu <yhlu.kernel@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jack Steiner <steiner@sgi.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>