add linux-nokia-n900 and remove linux-postmarketos-stable

The linux-nokia-n900 package is based on the linux-postmarketos-stable, same kernel version and same config.

I've removed a lot of unnecessary code for multiple architecture and -dev subpackage (I don't think somebody ever used it on the N900).

I've also added 2 patches from the maemo leste kernel:

• 0001-ARM-dts-n900-increase-charge-current-limit-to-950mA.patch
• 0002-ARM-dts-n900-remove-rx51-battery.patch

And added a patch to ignore the battery inaccurate flag, which indicates that the battery is not calibrated (requires full charge -> empty cycle to calibrate)

• 0003-power-supply-bq27xxx_battery-ignore-inaccurate-flag.patch

The battery driver in the original 2.6 kernel used in the Maemo Freemantle did not have this flag and the battery percentage wasn't that inaccurate.

Closes #464 (closed)