mmc: disable UHS modes if Vcc cannot be switched on and off

If a power cycle cannot be done on Vcc, it is safer not to try the UHS
modes because we wouldn't be able to recover from an error occurring
during the UHS initialization.

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>

include/mmc.h

@@ -544,6 +544,7 @@ struct mmc {
 	uint clock;
 	enum mmc_voltage signal_voltage;
 	uint card_caps;
+	uint host_caps;
 	uint ocr;
 	uint dsr;
 	uint dsr_imp;