i2c: i2c-mux-gpio: remove error messages for probe deferrals

Probe deferral is not an error case. It happens only when
the necessary dependencies are not there yet.

The driver core is already printing a message when a driver
requests probe deferral, so this can be traced in the logs
without these error prints.

This patch removes the error messages for these deferral cases.

Signed-off-by: Ionut Nicu <ioan.nicu.ext@nokia.com>
Acked-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Acked-by: Peter Korsgaard <peter.korsgaard@barco.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>