mfd: Fix tps65910 build failure

The tps65910_parse_dt() prototype for !CONFIG_OF was not correct, leading to:

drivers/mfd/tps65910.c: In function ‘tps65910_i2c_probe’:
drivers/mfd/tps65910.c:218:3: error: too many arguments to function ‘tps65910_parse_dt’

Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>