ARM: mach-shmobile: clock-r8a7740: use followparent_recalc on usb24s

If the clocks is always same value as the parent clock,
we can use followparent_recalc() for .recalc

Reported-by: Paul Mundt <lethal@linux-sh.org>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Simon Horman <horms@verge.net.au>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>