kdump.conf man page fixes
Fix the typos and grammar problems in kdump.conf man page.
Reported-by: Donald Berry <dberry@redhat.com>
Signed-off-by: Xunlei Pang <xlpang@redhat.com>
Signed-off-by: Dave Young <dyoung@redhat.com>
Acked-by: Baoquan He <bhe@redhat.com>