mmc: sdhci-sirf: constify sdhci_pltfm_data and sdhci_ops structures

The sdhci_pltfm_data structure is only passed as the second argument
of sdhci_pltfm_init, which is const, while the sdhci_ops structure
is only stored in the ops field of a sdhci_pltfm_data structure,
which is also const.  Thus both kinds of structures can be const as
well.

Done with the help of Coccinelle.

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>