crossystem: Fix mosys data length check
crossystem: Fix mosys data length check

CL:942031 introduced a check for the length of output returned by
mosys.  If the output has a trailing newline, then the check failed.
Just make sure we get at least as much data as we expect.

BUG=b:74439800
BRANCH=none
TEST=run crossystem on bob; no 'mosys returned hex data' errors

Change-Id: If678b201185dbda869e4e17abae314470f5cef4a
Signed-off-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/958286
Reviewed-by: Stefan Reinauer <0ab4fef0c228799b0c44e01c732054569b690b58@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot