kernel/generic: modify mtd related patches for 3.14

kernel/generic: modify mtd related patches for 3.14

Function register_mtd_parser always returned 0 (at least since v3.3)
before being changed to return void in v3.14-rc1~65^2~93 (mtd: make
register_mtd_parser return void), so it's not needed to check the
return value of this function. Also add __init flag to caller.

This fix compile errors in 3.14 kernel like:
drivers/mtd/mtdsplit_seama.c: In function 'mtdsplit_seama_init':
drivers/mtd/mtdsplit_seama.c:99:2: error: void value not ignored as it ought to be
  return register_mtd_parser(&mtdsplit_seama_parser);
  ^

Signed-off-by: Zhao, Gang <gamerh2o@gmail.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@40731 3c298f89-4303-0410-b956-a3cf2f4a3e73