ARM: OMAP2+: Drop unused pm-noop

Looks like these functions don't do anything in the mainline kernel so
we can just drop it.

Note that we must now also remove ir-rx51 pdata as it relies on the dummy
platform data that does not do anything. And ir-rx51 is calling a pdata
callback that doesn't do anything without checking if it exists first.

For configuring device specific minimal latencies, the interface to use
is pm_qos_add_request(). For an example, see what was done in commit
9834ffd1

 ("ASoC: omap-mcbsp: Add PM QoS support for McBSP to prevent
glitches"). I've added some comments to ir-rx51 so people using it can
add pm_qos support and test it.

Cc: Ivaylo Dimitrov <ivo.g.dimitrov.75@gmail.com>
Cc: Kevin Hilman <khilman@kernel.org>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Acked-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>