cmdline-parser: fix build

Fix following errors:

  include/linux/cmdline-parser.h:17:12: error: 'BDEVNAME_SIZE' undeclared here
  block/cmdline-parser.c:17:2: error: implicit declaration of function 'kzalloc'

Signed-off-by: Alexander Beregalov <alexander.beregalov@intel.com>
Cc: CaiZhiyong <caizhiyong@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>