fbdev: controlfb: Remove the unused function VAR_MATCH()

The function VAR_MATCH is defined in the controlfb.c file, but not
called elsewhere, so delete this unused function.

drivers/video/fbdev/controlfb.c:111:19: warning: unused function 'VAR_MATCH'.

Link: https://bugzilla.openanolis.cn/show_bug.cgi?id=2153


Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Signed-off-by: Jiapeng Chong <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Helge Deller <deller@gmx.de>