i2c: stm32f7: simplify status messages in case of errors

Avoid usage of __func__ when reporting an error message
since dev_err/dev_dbg are already providing enough details
to identify the source of the message.

Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Reviewed-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>