mmc: sdhci-pci: make guid intel_dsm_guid static

The guid intel_dsm_guid does not need to be in global scope, so make it
static.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>