scripts: Change QEMU binary name

`kvm` is a symlink to the `qemu-system-x86_64`. Use this name instead so
the script can be used on other distros without modification.

Signed-off-by: Tim Crawford <tcrawford@system76.com>

scripts/qemu.sh

@@ -17,7 +17,7 @@ then
 fi
 MODEL_DIR="$(realpath "models/${MODEL}")"
 
-kvm -M q35 -m 4096 -vga std \
+qemu-system-x86_64 -M q35 -m 4096 -vga std \
     -bios "build/${MODEL}/firmware.rom" \
     -chardev stdio,mux=on,id=debug \
     -device isa-serial,index=2,chardev=debug \