smbios: Refactor 32-bit code into an else statement

In preparation for adding support for SMBIOS3 move this code into an
else statement. There is no functional change.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Reviewed-by: Ilias Apalodimas <ilias.apalodimas@linaro.org>