platform/x86/amd: pmc: Add num_samples message id support to STB

platform/x86/amd: pmc: Add num_samples message id support to STB

Recent PMFWs have the support for S2D_NUM_SAMPLES message ID that
can tell the current number of samples present within the STB DRAM.

num_samples returned would let the driver know the start of the read
from the last push location. This way, the driver would emit the
top most region of the STB DRAM.

Co-developed-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Sanket Goswami <Sanket.Goswami@amd.com>
Signed-off-by: Shyam Sundar S K <Shyam-sundar.S-k@amd.com>
Link: https://lore.kernel.org/r/20230206150855.1938810-2-Shyam-sundar.S-k@amd.com
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>