lib: smbios: verify_checksum() is duplicate

The function verify_checksum() duplicates what table_compute_checksum()
does. Replace it. table_compute_checksum() is always compiled.

Fixes: 415eab06 ("smbios: add parsing API")
Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>