mmc: sdhci: Add platform suspend/resume hooks.

Some platforms require saving/restoring registers across suspend/resume;
this hook allows them to do that inside their driver.

Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
index ad265b9..f761f23 100644
--- a/drivers/mmc/host/sdhci.h
+++ b/drivers/mmc/host/sdhci.h
@@ -275,6 +275,8 @@
 	void	(*platform_reset_exit)(struct sdhci_host *host, u8 mask);
 	int	(*set_uhs_signaling)(struct sdhci_host *host, unsigned int uhs);
 	void	(*hw_reset)(struct sdhci_host *host);
+	void	(*platform_suspend)(struct sdhci_host *host);
+	void	(*platform_resume)(struct sdhci_host *host);
 };
 
 #ifdef CONFIG_MMC_SDHCI_IO_ACCESSORS