rmnet_ctl: Add IPC logging and optimizations

Add IPC logging to the rmnet_ctl driver.
Reduce RX buffer size to 256 bytes.
Not re-post RX buffers during SSR.
Fix a potential memory leak while supplying RX buffers.

Change-Id: Icb1b881f3386af09374fe6755f9418b9cfdb59df
Acked-by: Weiyi Chen <weiyic@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>