remoteproc: qcom: Rename Hexagon v5 modem driver

The qcom_q6v5_pil implements support for the self-authenticating modem
subsystem. With the introduction of other q6v5 based non-TZ based
remoteproc driver the current name is cause for confusion, so rename it
to be more specific.

No functional change.

Reviewed-by: Niklas Cassel <niklas.cassel@linaro.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>