unicore32: Split UniCore-F64 instruction helpers from helper.c

This patch just splits ucf64 instruction simulation helpers from
helper.c.
Also, two checkpatch warnings are solved.

v1->v2: adjust copyright information for new ucf64_helper.c

Signed-off-by: Guan Xuetao <gxt@mprc.pku.edu.cn>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
