trace: Use 64bit variable for start and len

tputq() requires variables to have 64bit width that's why make them 64bit
to clean alignment requirement.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/6edb34ef1f10010d2380f964fb6b4fb3dc257799.1694779918.git.michal.simek@amd.com