x86, kdump: Change crashkernel_high/low= to crashkernel=,high/low

Per hpa, use crashkernel=X,high crashkernel=Y,low instead of
crashkernel_hign=X crashkernel_low=Y. As that could be extensible.

-v2: according to Vivek, change delimiter to ;
-v3: let hign and low only handle simple form and it conforms to
	description in kernel-parameters.txt
     still keep crashkernel=X override any crashkernel=X,high
        crashkernel=Y,low
-v4: update get_last_crashkernel returning and add more strict
     checking in parse_crashkernel_simple() found by HATAYAMA.
-v5: Change delimiter back to , according to HPA.
     also separate parse_suffix from parse_simper according to vivek.
	so we can avoid @pos in that path.
-v6: Tight the checking about crashkernel=X,highblahblah,high
     found by HTYAYAMA.

Cc: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/1366089828-19692-5-git-send-email-yinghai@kernel.org
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/kernel/setup.c

@@ -528,7 +528,7 @@ static void __init reserve_crashkernel_low(void)
 	int ret;
 
 	total_low_mem = memblock_mem_size(1UL<<(32-PAGE_SHIFT));
-	/* crashkernel_low=YM */
+	/* crashkernel=Y,low */
 	ret = parse_crashkernel_low(boot_command_line, total_low_mem,
 						&low_size, &base);
 	if (ret != 0) {
@@ -542,7 +542,7 @@ static void __init reserve_crashkernel_low(void)
 		low_size = swiotlb_size_or_default() + (8UL<<20);
 		auto_set = true;
 	} else {
-		/* passed with crashkernel_low=0 ? */
+		/* passed with crashkernel=0,low ? */
 		if (!low_size)
 			return;
 	}
@@ -582,7 +582,7 @@ static void __init reserve_crashkernel(void)
 	ret = parse_crashkernel(boot_command_line, total_mem,
 			&crash_size, &crash_base);
 	if (ret != 0 || crash_size <= 0) {
-		/* crashkernel_high=XM */
+		/* crashkernel=X,high */
 		ret = parse_crashkernel_high(boot_command_line, total_mem,
 				&crash_size, &crash_base);
 		if (ret != 0 || crash_size <= 0)