qcacld-3.0: Remove hdd_device_mode_to_string()

qdf_opmode_str() has recently been added for converting a vdev operating
mode into a human readable string. Historically, HDD has used
hdd_device_mode_to_string() for this purpose. Replace
hdd_device_mode_to_string() with qdf_opmode_str() such that there is one
function for mapping vdev operating mode to human readable string.

Change-Id: I38880f915b617b5c02b2029762eacdf6ef8bac15
CRs-Fixed: 2336065
13 files changed