net: qualcomm: rmnet: Set pacing shift

The real device over which the rmnet devices are installed also
aggregate multiple IP packets and sends them as a single large
aggregate frame to the hardware. This causes degraded throughput
for TCP TX due to bufferbloat.

To overcome this problem, pacing shift value of 8 is set using the
sk_pacing_shift_update() helper. This value was determined based
on experiments with a single stream TCP TX using iperf for a
duration of 30s.

Pacing shift | Observed data rate (Mbps)
          10 | 9
           9 | 140
           8 | 146 (Max link rate)

CRs-Fixed: 2156182
Change-Id: I911bf2c26704458f752c79d301ca561fe7f1ffd7
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>