kdump: update elfcorehdr documentation to reflect supported architectures

IA64, PPC and SH also support the elfcorehdr command line.
Signed-off-by: NSimon Horman <horms@verge.net.au>
Acked-by: NVivek Goyal <vgoyal@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Documentation/kernel-parameters.txt

@@ -690,7 +690,7 @@ and is between 256 and 4096 characters. It is defined in the file
 			See Documentation/block/as-iosched.txt and
 			Documentation/block/deadline-iosched.txt for details.
 
-	elfcorehdr=	[X86-32, X86_64]
+	elfcorehdr=	[IA64,PPC,SH,X86-32,X86_64]
 			Specifies physical address of start of kernel core
 			image elf header. Generally kexec loader will
 			pass this option to capture kernel.