unix/mpconfigport.h: Remove obsolete MICROPY_FATFS_VOLUMES config.

unix/mpconfigport.h

@@ -134,9 +134,6 @@
 #define MICROPY_FATFS_OO               (1)
 #define MICROPY_FATFS_ENABLE_LFN       (1)
 #define MICROPY_FATFS_RPATH            (2)
-// Can't have less than 3 values because diskio.h uses volume numbers
-// as volume types and PD_USER == 2.
-#define MICROPY_FATFS_VOLUMES          (3)
 #define MICROPY_FATFS_MAX_SS           (4096)
 #define MICROPY_FATFS_LFN_CODE_PAGE    (437) /* 1=SFN/ANSI 437=LFN/U.S.(OEM) */
 #define MICROPY_VFS_FAT                (0)