mmc: sdhci-s3c: fix checkpatch error and warnings

This patch fixes the checkpatch error and warnings listed below:

ERROR: return is not a function, parentheses are not required
WARNING: Prefer pr_err(... to printk(KERN_ERR, ...
WARNING: quoted string split across lines
WARNING: line over 80 characters
WARNING: braces {} are not necessary for single statement blocks

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>