memblock: Fix include breakages caused by 24aa0788

24aa0788 (memblock, x86: Replace memblock_x86_reserve/free_range()
with generic ones) removed arch/x86/include/asm/memblock.h and dropped
its inclusion from include/linux/memblock.h which breaks other
architectures which depended on the generic memblock.h pulling in the
arch specific one.

However, the proper fix isn't adding back the asm inclusion.  memblock
doesn't have any arch dependent part and doesn't need arch specific
header file and asm/memblock.h files are either practically empty or
contain mostly unrelated arch specific stuff.

* In microblaze, sh, powerpc, sparc and openrisc, asm/memblock.h is
  either empty or just contains unused MEMBLOCK_DBG() macro.  Remove
  them.

* In arm and unicore32, asm/memblock.h contains arch specific stuff.
  Include it directly from its users.  It might be a good idea to
  rename the header file to avoid confusion.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: "H. Peter Anvin" <hpa@zytor.com>
Cc: Yinghai Lu <yinghai@kernel.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mundt <lethal@linux-sh.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>