drivers/video: Fix -Wstringop-truncation in hdmi.c

drivers/video: Fix -Wstringop-truncation in hdmi.c

Trying to copy into the string fields with strncpy() gives a warning from
gcc. Both fields are part of a packed HDMI header and do not require a
terminating \0 character.

../drivers/video/hdmi.c: In function 'hdmi_spd_infoframe_init':
../drivers/video/hdmi.c:230:2: warning: 'strncpy' specified bound 8 equals destination size [-Wstringop-truncation]
  230 |  strncpy(frame->vendor, vendor, sizeof(frame->vendor));
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
../drivers/video/hdmi.c:231:2: warning: 'strncpy' specified bound 16 equals destination size [-Wstringop-truncation]
  231 |  strncpy(frame->product, product, sizeof(frame->product));
      |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Just use memcpy() instead.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20201021121241.17623-1-tzimmermann@suse.de