platform/x86/amd/hsmp: Ensure sock->metric_tbl_addr is non-NULL

platform/x86/amd/hsmp: Ensure sock->metric_tbl_addr is non-NULL

If metric table address is not allocated, accessing metrics_bin will
result in a NULL pointer dereference, so add a check.

Fixes: 5150542b8ec5 ("platform/x86/amd/hsmp: add support for metrics tbl")
Signed-off-by: Suma Hegde <suma.hegde@amd.com>
Link: https://lore.kernel.org/r/20250807100637.952729-1-suma.hegde@amd.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>