mmc: sdhci-pci: Fix Braswell eMMC timeout clock frequency

Braswell eMMC host controller specifies an incorrect
timeout clock frequncy in the capabilities registers.
The correct value is 1 MHz.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>