i2c: Shrink struct i2c_client

This shrinks the size of "struct i2c_client" by 40 bytes:

 - Substantially shrinks the string used to identify the chip type
 - The "flags" don't need to be so big
 - Removes some internal padding

It also adds kerneldoc for that struct, explaining how "name" is really a
chip type identifier; it's otherwise potentially confusing.

Because the I2C_NAME_SIZE symbol was abused for both i2c_client.name
and for i2c_adapter.name, this needed to affect i2c_adapter too.  The
adapters which used that symbol now use the more-obviously-correct
idiom of taking the size of that field.

JD: Shorten i2c_adapter.name from 50 to 48 bytes while we're here, to
avoid wasting space in padding.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

drivers/i2c/busses/i2c-ixp2000.c

@@ -118,7 +118,7 @@ static int ixp2000_i2c_probe(struct platform_device *plat_dev)
 
 	drv_data->adapter.id = I2C_HW_B_IXP2000,
 	strlcpy(drv_data->adapter.name, plat_dev->dev.driver->name,
-		I2C_NAME_SIZE);
+		sizeof(drv_data->adapter.name));
 	drv_data->adapter.algo_data = &drv_data->algo_data,
 
 	drv_data->adapter.dev.parent = &plat_dev->dev;