This function's got its argument order chosen for "aesthetical"
reason of $(2) following $(1) in the macros but the logical order
is exactly the opposite: we care for kernel flavour much more than
for module set (which is dependent upon it).

So while silent dropout of kernel-image if KFLAVOURS is set
but KMODULES is empty could be fixed by testing for $(2) only,
it looks like a good time to fix this discrepancy altogether.