clk: probe common clock drivers earlier

Several SoCs implement platform drivers for clocks rather than
CLK_OF_DECLARE().  Clocks should come earlier because they are
prerequisites for many of other drivers.  It will help to mitigate
EPROBE_DEFER issues.

Also, drop the comment since it does not carry much value.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Michael Turquette <mturquette@baylibre.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>