mm/page_alloc.c: replace set_dma_reserve to set_memory_reserve

mm/page_alloc.c: replace set_dma_reserve to set_memory_reserve

Expand the scope of the existing dma_reserve to accommodate other memory
reserves too.  Accordingly rename variable dma_reserve to
nr_memory_reserve.

set_memory_reserve() also takes a new parameter that helps to identify if
the current value needs to be incremented.

Link: http://lkml.kernel.org/r/1470330729-6273-1-git-send-email-srikar@linux.vnet.ibm.com
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Suggested-by: Mel Gorman <mgorman@techsingularity.net>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
Cc: Hari Bathini <hbathini@linux.vnet.ibm.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>