i2c: Limit core locking to the necessary sections

The i2c-core code tends to hold the core lock for longer than it
should. Limit locking to the necessary sections for both performance
and clarity. This is also a requirement to support I2C multiplexers in
the future.

Signed-off-by: Jean Delvare <[email protected]>
Tested-by: Rodolfo Giometti <[email protected]>
Cc: David Brownell <[email protected]>
1 file changed