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 <[email protected]>
Signed-off-by: Yinghai Lu <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Acked-by: Vivek Goyal <[email protected]>
Signed-off-by: H. Peter Anvin <[email protected]>

Documentation/kernel-parameters.txt

@@ -603,16 +603,16 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			a memory unit (amount[KMG]). See also
 			Documentation/kdump/kdump.txt for an example.
 
-	crashkernel_high=size[KMG]
+	crashkernel=size[KMG],high
 			[KNL, x86_64] range could be above 4G. Allow kernel
 			to allocate physical memory region from top, so could
 			be above 4G if system have more than 4G ram installed.
 			Otherwise memory region will be allocated below 4G, if
 			available.
 			It will be ignored if crashkernel=X is specified.
-	crashkernel_low=size[KMG]
-			[KNL, x86_64] range under 4G. When crashkernel_high= is
-			passed, kernel could allocate physical memory region
+	crashkernel=size[KMG],low
+			[KNL, x86_64] range under 4G. When crashkernel=X,high
+			is passed, kernel could allocate physical memory region
 			above 4G, that cause second kernel crash on system
 			that require some amount of low memory, e.g. swiotlb
 			requires at least 64M+32K low memory.  Kernel would
@@ -620,7 +620,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 			This one let user to specify own low range under 4G
 			for second kernel instead.
 			0: to disable low allocation.
-			It will be ignored when crashkernel_high=X is not used
+			It will be ignored when crashkernel=X,high is not used
 			or memory reserved is below 4G.
 
 	cs89x0_dma=	[HW,NET]