ASoC: msm8974: Avoid multiple ocmem alloc requests during seek

This change adds specific condition for when to request
for ocmem region thus avoiding multiple ocmem alloc requests.
During seek the audio clip TRIGGER_START gets invoked without
TRIGGER_STOP, due to this a new ocmem request will be queued
without deleting the previous one. Add a condition to check
if there is already a pending request with ocmem. Ocmem disable
request will happen when the playback session is closed.

Change-Id: I3ddbebc57c18f4bb5e09fc3a9081f6a260a7a783
Signed-off-by: Phani Kumar Uppalapati <phanik@codeaurora.org>