[PATCH] I2C: i2c-vid.h: Support for VID to reg conversion

Adds conversion from VID (mV) to register value. Used by the atxp1 I2C module.
Removed uneeded switch case.

Signed-off-by: Sebastian Witt <se.witt@gmx.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>