video: s3c-fb: fix checkpatch errors and warning

This patch fixes the checkpatch errors listed below:

ERROR: space required before the open parenthesis '('
ERROR: need consistent spacing around '+' (ctx:WxV)
ERROR: space prohibited before that close parenthesis ')'

Also, following warning is fixed by adding 'platid' variable
which can reduce number of lines exceeding 80 characters.

WARNING: line over 80 characters

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>