samsung-p4note: use sparse image

Hi! I'm super excited to run pmOS on my N8010! 😸 The work done by all the people to support this device/arch even including mainline is really awesome.

It took me quite a while to make it boot though even though I am used to flashing LineageOS images on the device. (Maybe because pmOS on a real device is new to me.)

This MR should make everybody's life a bit easier since it enables users to

1. directly flash pmOS using pmbootstrap/heimdall without a hassle of transferring the rootfs img on to the device first using adb push / SD card and doing stuff in TWRP/recovery
2. and also allows to conveniently flash the image directly to a much bigger USERDATA partition, which is currently possible only in an even more inconvenient way.

The sparse image flashing works both from heimdall and from an external SD card via TWRP (if I didn't accidentally test something else).

I have a draft ready of an update of the Installation section of the wiki page Samsung Galaxy Note 10.1 (samsung-p4note) to make it more newbie-friendly which covers various workarounds that I came up with before I figured out this sparse image stuff and will publish the update depending on the result of this MR.

I hope it works for all the p4note targets, not just my N8010. 🤞