pmbootstrap doesn't consider underscores as part of codenames, so we'll
rename the device package to "laurel" instead of "laurel_sprout". Kernel
DTBs will keep the actual device name, since (at least from my
knowledge) it's accepted.
Since one of the goals of the postmarketOS project is to eventually use generic
kernels for most devices, renaming the linux package to use the name for
the SoC instead of the device name makes more sense in the long run and
for other people porting postmarketOS to other devices.