Robust port expander initialization

[Rahix]

Right now, most port expander implementations assume the device to be in its reset state. They do not check that all registers actually match expected values.

This is not robust because it can break horribly when a device isn't in its reset state for some reason (glitch, bad i2c transfer from other device, bug in our code, etc.).

Thus, let's augment all port expander drivers to properly set all important registers to their reset values during startup:

• MAX7321
• PCA9536
• PCA9538
• PCA9555
• PCF8574A
• PCF8574
• PCF8575
• TCA6408A
• PI4IOE5V6408