[media] em28xx-i2c: Fix error code for I2C error transfers

Follow the error codes for I2C as described at Documentation/i2c/fault-codes.

In the case of the I2C status register (0x05), this is mapped into:

	- ENXIO - when reg 05 returns 0x10
	- ETIMEDOUT - when the device is not temporarily not responding
		      (e. g. reg 05 returning something not 0x10 or 0x00)
	- EIO - for generic I/O errors that don't fit into the above.

In the specific case of 0-byte reads, used only during I2C device
probing, it keeps returning -ENODEV.

TODO: return EBUSY when reg 05 returns 0x20 on em2874 and upper.

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>