soc: qcom: smem: update max processor count

Update max processor count to reflect the number of co-processors on
SA8775P SoCs.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Eric Chanudet <echanude@redhat.com>
Tested-by: Eric Chanudet <echanude@redhat.com>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230209095753.447347-2-brgl@bgdev.pl