i2c: davinci: Fix bad dev_get_platdata() conversion

commit 6d4028c6 (i2c: use dev_get_platdata()) did a bad conversion
of this one case:

  drivers/i2c/busses/i2c-davinci.c: In function 'davinci_i2c_probe':
  drivers/i2c/busses/i2c-davinci.c:665:2: warning: passing argument 1 of
	'dev_get_platdata' from incompatible pointer type [enabled by default]

Reviewed-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Olof Johansson <olof@lixom.net>