postmarketos-initramfs: use dd to allocate logs image

fallocate seems to cause some strange behaviour where the logs.img file
is treated like it's empty. Given it's small and in a ramdisk let's just
create it with dd instead.

Signed-off-by: Caleb Connolly <caleb@postmarketos.org>

main/postmarketos-initramfs/init_functions.sh

@@ -823,7 +823,7 @@ create_logs_disk() {
 	local upload_file=""
 	echo "Creating logs disk"
 
-	fallocate -l 32M /tmp/logs.img
+	dd if=/dev/zero of=/tmp/logs.img bs=1M count=32
 	# The log device used is assumed to be $loop_dev
 	losetup -f /tmp/logs.img
 	mkfs.vfat -n "PMOS_LOGS" "$loop_dev"