msm: ipa: fix wrong usage and cleanup dead code

Couple of code cleanup
  - remove dead code
  - initialize local variables before use
  - validate gsi_ep_cfg_ptr return

Change-Id: Ia2c2a5559fa2c5f89b33cc1ff897df0faa725e7e
Signed-off-by: Mohammed Javid <mjavid@codeaurora.org>