soc: qcom: pmic_glink: add support for multiple pmic_glink devices

Currently, pmic_glink driver supports a single Glink channel of
name PMIC_RTR_ADSP_APPS. Add support for another Glink channel of
name PMIC_LOGS_ADSP_APPS through which logs or debug information
can be shared to HLOS from the remote subsystem.

As of now, pmic_glink rpmsg driver is registered when pmic_glink
platform driver is probed. This doesn't work well when multiple
pmic_glink devices need to be supported because of the way that
kernel device framework thinks the same rpmsg device is being
registered again. Fix this by registering pmic_glink platform
and rpmsg drivers from module_init().

Change-Id: Ia3a7777d39e94557e6cdf2d72675614581e67572
Signed-off-by: Subbaraman Narayanamurthy <subbaram@codeaurora.org>