Fix optee-os build

     * Remove the file generation and directly copy the files.

the files:
    default_regular.c
    default_regular.h

were generate with command line:
       $ scripts/render_font.py \
       --font_file lib/libutee/tui/fonts/amble/Amble-Regular.ttf \
       --font_size 20 --font_name default_regular \
       --out_dir out/arm-plat-rcar/ta_arm64-lib/libutee/tui

the files:
    default_bold.c
    default_bold.h
were generate with command line:
       $ scripts/render_font.py \
       --font_file lib/libutee/tui/fonts/amble/Amble-Bold.ttf \
       --font_size 20 --font_name default_bold
       --out_dir out/arm-plat-rcar/ta_arm64-lib/libutee/tui

python-wand 0.4.3 (and newer) is incompatible with imagemagick >= 7.0,
so we need to backport imagemagick 6.

If you don't have imagemagick 6 install on your host the build of optee-os
will failed.

Change-Id: I83a6c4b963b7d3e18f2730b601934708a2f6c7ef
Signed-off-by: Ronan Le Martret <ronan.lemartret@iot.bzh>