Merge the QorIQ GPIO drivers between arm and powerpc

[jhibbits]

Summary

They're nearly identical, so don't use two copies. Merge the newer
driver into the older one, and move it to a common location.

Add the Semihalf and associated copyrights in addition to mine, since
it's a non-trivial amount of code merged.

[mw]

Thank you Justin for doing the change!

sys/conf/files.arm64

106

It looks like some conflict resolution remainings slipped into the patch.

172

Please align 'optional' and the actual options with the entries above.

sys/dev/gpio/qoriq_gpio.c

406

(While not having the docs in hand) sys/arm64/qoriq/ls1046_gpio.c did not use GPIO_GPIBE - this could be a bug, but:

• is above configuration required for the input mode?
• isn't it problematic in case of non-input modes?

[jhibbits]

sys/conf/files.arm64

106

Oops. Must've snuck in during a rebase.

sys/dev/gpio/qoriq_gpio.c

406

This is required for LX2160, but may not be required for others.

Every reference I have, for P1022, P5020, and LX2160, any unimplemented registers in this block are ignored, so it's not a problem on other targets. I don't yet have a Honeycomb board, so have only tested on a P1022 board thus far, that it's not broken.

This only affects pins marked as input, it has no effect on other pins.

This is set 'unconditionally' (only conditional on compatible property) in Linux, too.

[jhibbits]

Address @mw's feedback.