rombios/tcgbios: initialise logdataptr in HashLogEvent32

rombios/tcgbios: initialise logdataptr in HashLogEvent32

Gcc complains:

tcgbios.c: In function ‘HashLogEvent32’:
tcgbios.c:1131:10: error: ‘logdataptr’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
    entry = tcpa_extend_acpi_log(logdataptr);

It fails to figure out when logdataptr is used it is always initialised
in a if block a few line above.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>