msm: qdsp5: Avoid race condition of init info cmd being sent multiple times

GET_INIT_INFO command is sent to modem adsp service to get the information
such as task/queues supported by adsp. This command is sent whenever
msm_adsp_get() is called first time by any decoder/encoder drivers. This
command needs to be sent only once, to achieve this a global flag
init_info_cmd_sent is set in msm_get_adsp() after sending GET_INIT_INFO
command to adsp services. Currently flag init_info_cmd_sent is not
protected by any lock. Hence there is chance of GET_INIT_INFO command
being sent multiple times if there are concurrent calls to msm_adsp_get()
where each caller observes flag init_info_cmd_sent not to be set.

Fix this by protecting adsp info initialization sequence with mutex.

Change-Id: Ib0bd865d44e4687f9a85b56854e1fd3277a5707d
Signed-off-by: Manish Dewangan <manish@codeaurora.org>