Revert "net: stmmac: fix build failure due to missing COMMON_CLK dependency"

This reverts commit bde49753

.

All legacy clock implementations now implement clk_set_rate() (Some
implementations may be dummies, though).

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arnd.de>
Acked-by: Jose Abreu <joabreu@synopsys.com>
Signed-off-by: David S. Miller <davem@davemloft.net>