clk: rename CONFIG_SPL_CLK_SUPPORT to CONFIG_SPL_CLK

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Stefano Babic <sbabic@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>