TI:armv7: Move CONFIG_SPL_LIBDISK_SUPPORT to MMC section

We only need this library when we're doing "disk" access to MMC/SD.
Update comment around the rest of CONFIG_SPL_LIB* to note that the
others are always required.

Signed-off-by: Tom Rini <trini@ti.com>

include/configs/ti_armv7_common.h

@@ -223,14 +223,14 @@
 #endif
 
 #ifdef CONFIG_MMC
+#define CONFIG_SPL_LIBDISK_SUPPORT
 #define CONFIG_SPL_MMC_SUPPORT
 #define CONFIG_SPL_FAT_SUPPORT
 #endif
 
-/* General parts of the framework. */
+/* General parts of the framework, required. */
 #define CONFIG_SPL_I2C_SUPPORT
 #define CONFIG_SPL_LIBCOMMON_SUPPORT
-#define CONFIG_SPL_LIBDISK_SUPPORT
 #define CONFIG_SPL_LIBGENERIC_SUPPORT
 #define CONFIG_SPL_SERIAL_SUPPORT
 #define CONFIG_SPL_GPIO_SUPPORT