serial: sh_sci: remove HAVE_CLK build dependecy

Since 93abe8e4 (clk: add non CONFIG_HAVE_CLK routines) code using clk.h
like this driver needs not depend on HAVE_CLK.

Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>