media: atomisp: reduce the risk of a race condition

This driver is really on bad shape. One of the problems
is that, as soon as the I2C transfers start to happen, it
timeouts detecting a camera:

	ov2680 i2c-OVTI2680:00: ov2680_probe: ACPI detected it on bus ID=CAM1, HID=OVTI2680
	atomisp-isp2 0000:00:03.0: no camera attached or fail to detect
	ov2680 i2c-OVTI2680:00: gmin: initializing atomisp module subdev data using PMIC regulator
	...

The right fix here would be to use defer probe, but driver is
still on too bad shape.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>