drivers: rmnet: shs: Check backlog on all flushes

Checking for backlog will no longer occur for
only cpus with segmented flows. Backlog NET_RX switching
will now be checked for on every silver CPU regardless if
segmented flows are available.

Change-Id: Ic6912e9c3ddd719cb9b0f5b13609ba7161d31b1f
Acked-by: Raul Martinez <mraul@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>