staging: sm7xxfb: cleanup on smtc_alloc_fb_info

This patch improves coding style on smtc_alloc_fb_info.

Tested with SM712.

Signed-off-by: Javier M. Mellid <jmunhoz@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>