OMAP4 has module specific context lost registers which makes it now
possible to have module level context loss count, instead of relying
on the powerdomain level context count.

Add 2 private hwmod api's to update/clear the hwmod/module specific
context lost counters/register.

Update the module specific context_lost_counter and clear the hardware
bits just after enabling the module.

omap_hwmod_get_context_loss_count() now returns the hwmod context loss
count them on platforms where they exist (OMAP4), else fall back on
the pwrdm level counters for older platforms.
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
[paul@pwsan.com: added function kerneldoc, fixed structure kerneldoc,
 rearranged structure to avoid memory waste, marked fns as OMAP4-specific,
 prevent fn entry on non-OMAP4 chips, reduced indentation, merged update
 and clear, merged patches]
[t-kristo@ti.com: added support for arch specific hwmod ops, and changed
 the no context offset indicator to USHRT_MAX]
Signed-off-by: Tero Kristo <t-kristo@ti.com>
[paul@pwsan.com: use NO_CONTEXT_LOSS_BIT flag rather than USHRT_MAX;
 convert unsigned context lost counter to int to match the return type;
 get rid of hwmod_ops in favor of the existing soc_ops mechanism;
 move context loss low-level accesses to the PRM code]
Signed-off-by: Paul Walmsley <paul@pwsan.com>