OMAP2+: powerdomain: add pwrdm_can_ever_lose_context()

OMAP2+: powerdomain: add pwrdm_can_ever_lose_context()

Some drivers wish to know whether the device that they control can
ever lose context, for example, when the device's enclosing
powerdomain loses power.  They can use this information to determine
whether it is necessary to save and restore device context, or whether
it can be skipped.  Implement the powerdomain portion of this by
adding the function pwrdm_can_ever_lose_context().  This is not for
use directly from driver code, but instead is intended to be called
from driver-subarch integration code (i.e., arch/arm/*omap* code).

Currently, the result from this function should be passed into the
driver code via struct platform_data, but at some point this should
be part of some common or OMAP-specific device code.

While here, update file copyrights.

Signed-off-by: Paul Walmsley <paul@pwsan.com>