dt-bindings: remoteproc: qcom: Update Q6V5 Modem PIL binding

Add a new modem compatible string for QTI SC7280 SoCs and introduce the
"qcom,ext-regs" and "qcom,qaccept-regs" properties needed by the modem
sub-system running on SC7280 SoCs.

Signed-off-by: Sibi Sankar <sibis@codeaurora.org>
Acked-by: Rob Herring <robh@kernel.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/1631886935-14691-4-git-send-email-sibis@codeaurora.org