firmware: dmi_scan: Use full dmi version for SMBIOS3

New SMBIOS3 spec adds additional field for versioning - docrev.
The docrev identifies the revision of a specification implemented in
the table structures, so display SMBIOSv3 versions in format,
like "3.22.1".

In case of only 32 bit entry point for versions > 3 display
dmi version like "3.22.x" as we don't know the docrev.

In other cases display version like it was.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>