ARM: OMAP2+: Cleanup omap_mcbsp_dev_attr and other legacy data

The omap_mcbsp_dev_attr data was used to supply instance-specific
data for legacy non-DT devices. The legacy McBSP device support
including the usage of the hwmod class revision data has been
dropped in commit 48f66937 ("ARM: OMAP2+: Remove unused legacy
code for McBSP") and this data is therefore no longer needed.
So, cleanup the structure and all the associated data in various
hwmod data files.

Cc: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>