platform/x86: amd-pmc: uninitialized variable in amd_pmc_s2d_init()

The "size" variable can be uninitialized if amd_pmc_send_cmd() fails.

Fixes: 3d7d407d ("platform/x86: amd-pmc: Add support for AMD Spill to DRAM STB feature")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20220307141832.GA19660@kili


Signed-off-by: Hans de Goede <hdegoede@redhat.com>