mfd: Convert struct i2c_msg initialization to C99 format

Convert the struct i2c_msg initialization to C99 format. This makes
maintaining and editing the code simpler. Also helps once other fields
like transferred are added in future.

Thanks to Julia Lawall <julia.lawall@lip6.fr>  for automating the conversion

Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>