msm: ipc_logging: Add ipc logging context destroy API

If IPC logging gets used by other drivers and modules, then those
drivers/modules may need to destroy the logging context for dynamic
modules that get unloaded.

Add a function called ipc_log_context_destroy() that will destroy a
logging context created by ipc_log_context_create().

Change-Id: I0f927235e51bd17b82bb2bd2eea198fc681e03cd
Signed-off-by: Arun Kumar Neelakantam <aneela@codeaurora.org>