kernel: Enable frontswap

kernel: Enable frontswap

"Frontswap provides a “transcendent memory” interface for swap pages. In
some environments, dramatic performance savings may be obtained because
swapped pages are saved in RAM (or a RAM-like device) instead of a swap
disk."

https://www.kernel.org/doc/html/latest/vm/frontswap.html

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
Acked-by: Peter Müller <peter.mueller@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>