spi/dw_spi: Fix dw_spi_mmio to depend on HAVE_CLK

dw_spi_mmio is dependent on the clock framework. This marks it as such
in Kconfig.

Signed-off-by: Jean-Hugues Deschenes <jean-hugues.deschenes@octasic.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>