net: stmmac: Fixing KW errors

- Fixing various types of kw errors.
List of KW
1. Suspicious dereference of pointer
before NULL check at dwmac-qcom-ethqos.c: 1396

2.Suspicious dereference of pointer
before NULL check at dwmac-qcom-ethqos.c: 1354

3.Suspicious dereference of pointer
before NULL check at dwmac-qcom-ethqos.c: 423

4.Suspicious dereference of pointer
before NULL check at dwmac-qcom-ethqos.c: 443

5.Suspicious dereference of pointer
before NULL check at dwmac-qcom-ethqos.c: 1683

6.Uninitialized variable is used at
dwmac-qcom-pps.c: 46.

Change-Id: I3c98c804c0fee2ecc291852e38a104ca12c42dcc
Acked-by: Nagarjuna Chaganti <nchagant@qti.qualcomm.com>
Signed-off-by: Suraj Jaiswal <jsuraj@codeaurora.org>