serial: sc16is7xx: change EFR lock to operate on each channels

serial: sc16is7xx: change EFR lock to operate on each channels

Now that the driver has been converted to use one regmap per port, change
efr locking to operate on a channel basis instead of on the whole IC.

Fixes: 3837a0379533 ("serial: sc16is7xx: improve regmap debugfs by using one regmap per port")
Cc:  <[email protected]> # 6.1.x: 3837a03 serial: sc16is7xx: improve regmap debugfs by using one regmap per port
Signed-off-by: Hugo Villeneuve <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>