ARM: S3C24XX: s3c24xx_mci_set_platdata should be marked __init

The s3c24xx_mci_set_platdata() is init time only, so should
be marked as __init

Signed-off-by: Arnaud Patard <arnaud.patard@rtp-net.org>
[ben-linux@fluff.org: update description]
Signed-off-by: Ben Dooks <ben-linux@fluff.org>