kexec: fix omitting offset in extended crashkernel syntax

Setting
 "crashkernel=512M-2G:64M,2G-:128M"
does not work but it turns to work if it has a trailing-whitespace,
like
 "crashkernel=512M-2G:64M,2G-:128M ".

It was because of a bug in the parser, running over the cmdline.

This patch adds a check of the termination.
Reported-by: Jin Dongming <jin.dongming@np.css.fujitsu.com>
Signed-off-by: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Tested-by: Jin Dongming <jin.dongming@np.css.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kexec.c

@@ -1228,7 +1228,7 @@ static int __init parse_crashkernel_mem(char 			*cmdline,
 	} while (*cur++ == ',');
 
 	if (*crash_size > 0) {
-		while (*cur != ' ' && *cur != '@')
+		while (*cur && *cur != ' ' && *cur != '@')
 			cur++;
 		if (*cur == '@') {
 			cur++;