Runtime PM lock init API right now returns pointer to a context
but this would cause confusion to the caller if feature is not
defined and dummy function return NULL as caller can't find real
failure versus dummy function returning because feature not being
enabled.
Fix declaring a data structure in QDF layer that caller can use
but it hides the internal details of HIF implementation for
Runtime PM locks.
CRs-fixed: 1116509
Change-Id: I4dcba604e803faa0e14fac6403610391895e382e
65b0eaa24b