ARM: OMAP: mcbsp: Implement generic register access

Register access can be made more generic by calculating register address
offsets runtime from common register definitions and by using reg_size and
reg_step variables that are passed via platform data. Common register
definitions are possible since McBSP registers are ordered similarly between
OMAP versions.

Remove also references to OMAP2+ specific config_type variable from generic
McBSP code since other variables and feature flags are better to carry needed
information from platform code.

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>