samsung-coreprimevelte: flashing, WiFi and sudden reboot fixes

Specifically, this MR does the following:

• Set deviceinfo_flash_sparse_samsung_format to "1" to allow the device to be fully flashed using Heimdall.
• Add a sysctl configuration file to stop the device from rebooting every few minutes. (This could also be done for the samsung-xcover3lte instead of the currently used initfs hook)
• Enable using xcover3lte's WiFi firmware.
• Since xcover3lte's WiFi firmware package should work for all PXA1908 devices, I have also renamed the package to firmware-samsung-pxa1908 to reflect that.

Open questions:

• Should device-samsung-xcover3lte be pkgrel bumped because I have renamed one of its dependencies? (Yes, needed to pass CI)
• Should device-samsung-coreprimevelte be pkgrel bumped only once (because the fixes will be merged in one MR) rather than thrice (which I did because 3 commits which changed device-samsung-coreprimevelte)?

cc @blacksilver