chromeos: vpd: properly null terminate values

chromeos: vpd: properly null terminate values

VPD strings are not null terminated, so we can't use strcpy
on them in cros_vpd_gets.

BUG=none
BRANCH=none
TEST=add serial_number followed by cam_calib_data to VPD on smaug;
make sure that smaug boots and serial number matches exactly (no garbage)

Change-Id: Id72885517b3d0b1934ba329c1ef0d89a67bd2bb4
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: 56bbe6688b11043360a046a250d1ea93db4d9f0e
Original-Change-Id: I811dfc2f0830a91410eb69961a6565080ff78267
Original-Signed-off-by: Stephen Barber <smbarber@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/280836
Original-Reviewed-by: David Hendricks <dhendrix@chromium.org>
Original-Reviewed-by: Benson Leung <bleung@chromium.org>
Reviewed-on: http://review.coreboot.org/10627
Tested-by: build bot (Jenkins)
Reviewed-by: Furquan Shaikh <furquan@google.com>
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>