qcacld-3.0: hdd: Refactor wlan_startup (phase 4)

In HDD, hdd_wlan_startup which is called by probe is beast of a
function to maintain. Over time it has grown to such an extent
that it is almost 800 lines of code with in a single function.
Divide the beast into logical smaller functions.

Fix style issues like conditional compilation with in the
function and other minor ones.

Change-Id: Iec2dc3aac934bbb90b87d4e8581e877e5b0a561c
CRs-fixed: 959287