ARM: davinci: remove unused davinci-i2s pdata

The davinci-i2s driver ("davinci-mcbsp") does not use platform
data any longer. Remove the dummy pdata provided by the board
drivers dm355, dm365, dm644x and neuros-osd2.

Signed-off-by: Petr Kulhavy <petr@barix.com>
Reviewed-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>