ARM: OMAP: mcbsp: Make wakeup control generic

Currently wakeup control code is compiled only when CONFIG_ARCH_OMAP3 is
set even it should be available for CONFIG_ARCH_OMAP4 only builds also.

Fix this by making wakeup control generic so that it is executed whenever
new feature flag has_wakeup in platform data is set. Currently flag is set
for McBSP config types 3 and 4.

Remove also old comments about idle mode settings and HW bug workarounds
that were not updated during hwmod conversion.

Signed-off-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Acked-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: Janusz Krzysztofik <jkrzyszt@tis.icnet.pl>
Signed-off-by: Tony Lindgren <tony@atomide.com>