i2c: stm32: change deprecated constant

Use of SECONDARY in DEVICE_AND_API_INIT is now deprecated and should
be replaced by POST_KERNEL

Change-Id: I543ae70e493527e75b4a4bcb9191475065b49166
Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
1 file changed