mm/cma.c: change pr_info to pr_err for cma_alloc fail log

It was observed that under cma_alloc fail log, pr_info was used instead
of pr_err.  This will lead to problems if printk debug level is set to
below 7.  In this case the cma_alloc failure log will not be captured in
the log and it will be difficult to debug.

Simply replace the pr_info with pr_err to capture failure log.

Link: http://lkml.kernel.org/r/1507650633-4430-1-git-send-email-pintu.ping@gmail.com
Signed-off-by: Pintu Agarwal <pintu.ping@gmail.com>
Cc: Laura Abbott <labbott@redhat.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Jaewon Kim <jaewon31.kim@samsung.com>
Cc: Doug Berger <opendmb@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/cma.c

@@ -461,7 +461,7 @@ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align,
 	trace_cma_alloc(pfn, page, count, align);
 
 	if (ret && !(gfp_mask & __GFP_NOWARN)) {
-		pr_info("%s: alloc failed, req-size: %zu pages, ret: %d\n",
+		pr_err("%s: alloc failed, req-size: %zu pages, ret: %d\n",
 			__func__, count, ret);
 		cma_debug_show_areas(cma);
 	}