mx6sabre_common.h: remove deprecated mmc open/close

Replace "mmc open/close" with "mmc dev" in mx6sabre_common.h as those commands
were removed with this commit: 614b2bf1c9

    cmd_mmc.c: Drop open/close mmc sub-commands

Signed-off-by: Maxin B. John <maxin.john@enea.com>
Acked-by: Otavio Salvador <otavio@ossystems.com.br>

include/configs/mx6sabre_common.h

@@ -111,12 +111,10 @@
 			"setenv get_cmd tftp; " \
 		"fi; " \
 		"if ${get_cmd} ${update_sd_firmware_filename}; then " \
-			"if mmc dev ${emmcdev} && " \
-				"mmc open ${emmcdev} 1; then "	\
+			"if mmc dev ${emmcdev} 1; then "	\
 				"setexpr fw_sz ${filesize} / 0x200; " \
 				"setexpr fw_sz ${fw_sz} + 1; "	\
 				"mmc write ${loadaddr} 0x2 ${fw_sz}; " \
-				"mmc close ${emmcdev} 1; " \
 			"fi; "	\
 		"fi\0"
 #else